Indoor Plant Lighting

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Indoor Plant Lighting

Types of Lights

Light and Colour

Natural Sunlight

Incandescent Lighting

Fluorescent Lighting HID/VHID Lamps

TYPES OF LIGHTS

Introduction

There are a number of different approaches used for growing plants under lights. Tomake an informed decision as to what type of lighting should be employed, thefundamentals of light, colour and lighting systems should be understood. In thisarticle we will examine the how light is qualitatively appraised with respect to colorand intensity. Different lighting systems will be examined, and most available types

of lights will be discussed. Examples of some "real world" lighting systems will begiven and analyzed with respect to effectiveness, initial cost, operating expense andlongevity.

LIGHT AND COLOUR

What is light

Visible light is that part of the electro-magnetic spectrum that lies between thewavelengths of ultraviolet and infrared. That's probably more that you need to knowfor the purposes of home growing.

White light is all colors

When we see a rainbow, we are seeing white light split up into it's componentcolours, hence the expression "all the colours of the rainbow". Plants, in general,absorb red and blue light and reflect green light. Our eyes are most sensitive to thecolor green.

Sunlight is different in different places in the world

Sunlight contains, more or less, equal portions of all colours of sunlight. Northernsunlight, that is, sunlight in areas north of the fortieth parallel, has more blue thanequatorial sunlight because of absorption of all other colours, or wavelengths of light,by the atmosphere.

This is the same effect that causes underwater photos taken below three feet to beso blue. Just as the atmosphere absorbs non-blue light so does water, except water
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absorbs non-blue light at a much greater rate. Almost all non-blue light below threefeet of water is absorbed.

How is light measured?

Light quality is expressed and measured in many ways. Light colour can be measured

in degrees Kelvin (K) and the colour rendering index of a light source can bemeasured and expressed as CRI. (0 degrees Celsius = 273 degrees Kelvin; 0 degreesKelvin = absolute zero)

Colour temperature - degrees Kelvin

White light can have different "warmths". A bit more red/yellow makes white lightappear "warmer". A bit more blue and light appears "cool". This can be quantitativelyassessed by the assigning of a colour temperature, given in degrees Kelvin. Think ofcolour temperature as the colour of a block of iron as it is heated to various hightemperatures. A warm, reddish light is around 3500 degrees Kelvin, and above 6000degrees Kelvin the light takes on a bluish tone. Sunlight is somewhere around 5000degrees Kelvin.

Colour rendering index (CRI)

The colour rendering index identifies the degree of colour shift objects undergo whenilluminated by a particular light source compared to a standard source. In simplerterms, the CRI expresses the degree to which a light source renders the true colourimpression. The CRI is an index and ranges from 0 to 100. A light source having a CRIof 100 means objects illuminated by it look like they're supposed to; that is theirnatural color is not distorted. A light source having a very low CRI would tend tomake objects appear to be a different shade or even colour that they really are. Anexample of light with a high CRI is, obviously, sunlight. Some fluorescent tubes suchas Daylight, Chroma 65 or Vita-Lite have a very high CRI. Some light sources such as

Gro-Lux or sodium vapour lamps have very low CRI's.

The color rendering is important when examining flowers under different light.Because cool white (blue) fluorescent lights lack red, red flowers look dull, almostgrayish. Sodium or mercury lights are even worse for distorting color.

Light Meters

A light meter may be used to measure the amount of light, measured in foot-candles,emitted by a light source, measured at some distance from the source. Growinginformation for a plant will give an indication of the amount of light the plantrequires, usually stated in foot candles at the surface of the leaf.

Light meters for use in photography are designed to be sensitive to the samewavelengths as the human eye. That is not what a plant sees! To measure correctlywhat a plant sees, you must use a meter that provides a measure ofphotosynthetically active radiation (PAR), the wavelengths of light most important forplant health. These wavelengths, between 400 and 700 nanometers, are critical forthe photosynthesis and chlorophyll production that drive plant growth. (A nanometeris one billionth of a meter.)

NATURAL SUNLIGHT


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Good light, free, but hard to control

This is of course what plants are used to and it can hardly be argued that this isanything less than the most natural. However coaxing enough sunlight onto yourplants throughout the whole year from the top rather than from the side as through awindow can be problematical.

Sunlight is the certainly the cheapest way to illuminate your plants, although it isunreliable and very difficult to regulate. This is subject to geographical variation, ofcourse. If you live in California and have a skylight over a plant stand, you might begetting enough light. If however you live in an area that does not get a lot of sunlightor your plants are stacked in rows in a basement, you will obviously needsupplemental lighting.

INCANDESCENT LIGHTING

Cheap, low quality light

Incandescent lights are the ubiquitous screw-in bulbs you most likely have lightingyour home. An incandescent bulb consists of a glass bulb with a tungsten filament ina near vacuum; just a small amount of argon or krypton is present. When currentflows through the filament, it heats up and glows giving off both heat and light.

Halogen bulbs

A variation of the incandescent bulb is the halogen bulb. This is an improvement toincandescent bulbs invented by GE in 1958 for the wing tip navigation lights of theBoeing 707. In a regular incandescent bulb, the tungsten filament evaporates, andover time the inside of the bulb is coated with a fine coat of tungsten from condensedtungsten vapour. This coating will severely limit the light output of the bulb. In ahalogen bulb, a small amount of one of the halogens (Iodine or Bromine are used) is

present and combines with the evaporated tungsten. This Tungsten Iodide orTungsten Bromide molecule has an affinity for the tungsten filament and returnsthere and splits. The tungsten from this molecule returns to the filament while thehalogen returns to the atmosphere inside the bulb. This process does not work unlessthe bulb jacket is at least 200 degrees Celsius. This is why halogen lamps are so hotand must be taken into consideration. Halogen lamps are 25-30% brighter thanregular incandescent bulbs. The halogen cycle, as it is called, takes place in a verysmall capsule, as it is easier to maintain the high temperature required for thehalogen cycle to operate in a smaller space. This capsule is placed inside anotherglass capsule which serves as the bulb's outer casing and although it is still plentyhot, it is not as hot as 200 degrees Celsius.

Output spectrum is biased towards the red

The output spectrum of incandescent light, halogen or regular, is biased heavilytoward the red. Non-halogen bulbs have a colour temperature of 2700K, whilehalogen bulbs have a colour temperature of 3000K - they are a slightly more whitishlight. Both have a CRI of 100. A diagram of the spectrum looks rather like a triangle,starting with almost no output in the green and rising at an almost linear rate to thefar red and infra-red. Although incandescent bulbs are very inefficient, they are avery good source of near and far red light which is certainly very important. They are


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sometimes used as supplements in systems which are deficient in the red end of thespectrum.

Efficiency

The great disadvantage to incandescent lights is their inefficiency - you don't get a

lot of light compared with how much energy you put apply. One saving grace in thisrespect is that the efficiency increases proportionally to the wattage, for example asingle 100 watt bulb is much brighter than two 50 watt bulbs. The energy that doesnot get converted to light is wasted by being given off as heat. All but the smallestwattage bulbs can generate an awful lot of heat, and this must be taken intoconsideration. Another point to consider is, because the heat is so great, a splash ofwater on a hot bulb can shatter it.

Halogen bulbs are more efficient than "regular" incandescent bulbs by virtue ofremaining brighter longer; they still give off 95% of their initial light output at the endof their lives, which are about twice as long as regular incandescent bulbs. They arealso more expensive.

The great advantage of non-halogen bulbs is of course their extreme low cost forinitial purchase, and of course their great availability; you can buy them anywhere.Halogen bulbs are on the average 5 to 10 times as expensive as their non-halogencounterparts and can usually be found at larger hardware stores. Since their primarymarket is yuppie track lighting they are usually found as spot or flood lights. Ofpotential interest to grower is the low voltage bulbs used in some track lightingsystems. Operating as 12V, these bulbs are quite small and would be good to use asupplemental light augmenting a fluorescent setup. They are also the cheapest ofhalogen bulbs. While I have seen them at $30 each in fancy designer light stores, Ihave also seen them in Price Club at 3 for $12. Sylvania makes a series of bulbscalled Capsylite that come in "regular" bulb shapes plus the large parabolic reflectorssometimes used to illuminate the outside of houses. Osram makes a large array ofdifferent shapes and sizes, most of which look like the vacuum tubes. They are

probably the most useful to growers because of their smaller size and wide range ofwattages; from low power bulbs all the way up to 150 watts. They are however notcheap and can be quite a challenge to find somewhere that stocks them.

Longevity

Incandescent bulbs have a lifespan of about 1000 hours. Halogen bulbs have a life ofabout 2000 hours. One interesting personal note here; although regular incandescentlights are rated at 1000 hours, we've all had some bulbs that seem to burn onforever. The Guinness book of world records lists the longest lasting light bulb asbeing an incandescent bulb in a firehouse in, I believe Boston that is some 70+ yearsold; it is never turned off, which is a key point. This is why your parents always gaveyou hell for flicking the lights on and off really quickly, the wear on the filament fromhaving current suddenly shot through it is quite great. If you'll notice, most bulbs failwhen turned on, not in the middle of operation, or when they are turned off. Thehalogen bulbs I have throughout my home seem to be on a timer; when 2000 hoursis up *poof*, they expire. I curse them out, do a rough calculation and come to theconclusion that their 2000 hours just expired.

FLUORESCENT LIGHTING


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This is a bunch of data on the commonly available fluorescent tubes from GE,Sylvania and Philips.

Cheaper To Run, More Expensive To Install

Fluorescent lights are very common in our day to day lives. They are cheap to

operate as they emit about four times as much light per unit of electricity asincandescent lights do. On the other hand they are more complicated to installbecause they require a ballast to operate. You may be familiar with the regular "coolwhite" and "warm white" tubes sold in hardware stores but what you may not know isthat fluorescent tubes come in hundreds of shapes, sizes and spectral output.

How They Work

Fluorescent lights work by placing an anode and a cathode at opposite ends of aglass tube. Inside the tube is a partial vacuum and a small amount of mercuryvapour. When energized, the mercury vapour is ionized and emits ultravioletradiation. The inside of the tube is coated with a phosphor - a powder that"fluoresces" (gives off light) when stimulated by ultraviolet radiation, thus producing

visible light. The chemical composition of the phosphor determines the spectrum orcolour of the emitted light. (Fluoresce has nothing to do with flour.)

Replace Tubes Every Six Months

Although fluorescent lights are very energy efficient, there is a particularly nastyphenomenon known as "cathode decay" that causes, over time, less energy to betransferred through the mercury vapour. The net effect is that the tube will emit lessand less light as it gets older. To all appearances, the tube will put out the sameamount of light until it suddenly stops dead one day, (which can take years), but forall practical purposes, because the drop off in light output is an exponential decay,the tube should optimally be replaced every six months or at the very least once a

year. Writing the installation date on the tube itself with a permanent magic markercan be a big help here.

Types Of Fluorescent Tubes

There are many different types of fluorescent tubes. They differ in the physical size,composition of the phosphor and the wattage. When fluorescent tube is mentioned,the standard T12 four foot tubes usually comes to mind. This tube has a diameter of1.5 inches and is available in 18", 24" 36", 48", 72" and 96" lengths. T12 tubes areavailable in HO (High Output) or VHO (Very High Output) which draw more and muchmore current respectively, but produce more light than regular T12 tubes. T12 tubesare also available in U-shaped, that is a four foot tube is bent back on itself so itforms a large U, and is about 24" long. The T8 or "slimline" fluorescent has a 1"

diameter tube and is available in 24", 36" and 48" lengths. Circular tubes areavailable with several different radii, and in several different types. In the last fewyears, compact fluorescent tubes have become very popular mostly as replacementsfor incandescent bulbs. These tubes come in all sizes, from a 3" 5 watt bulb to muchlarger bulbs that replace 40W four foot tubes, yet are just one third of the size.

The phosphor chemistry is what makes the difference between a cool white and adaylight tube and every tube is available with a dizzying array of choices in this area.
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As the composition of the phosphor changes so does the spectrum of the visible lightbeing emitted by the tube.

For illumination for plant growth only a small percentage of the dozens of availabletubes are appropriate. They fall into the following broad categories: industrial, fullspectrum, daylight, plant growth, actinic, tri-phosphor, special purpose and HO/VHO.

Use Four Foot Tubes

Although fluorescent tubes come in many sizes, volume of scale dictates that there isreally only one size - the T12 four foot length. Some ninety percent of all fluorescenttubes made are this size, and because of this volume this is the cheapest size,although this needs to be qualified. If you are buying tubes through normal retailchannels, the markup is generally high enough that they can play with prices and a24 inch tube costs less than a 48 inch tube but more than an 18 inch tube. If howeveryou are buying tubes through other channels, such as lighting distributors, you mayfind that the four foot tube is cheaper than any other size. T12 tubes that are smalleror larger will cost you more. Additionally, the four foot size has the longest lifespanand also the highest ratio of lumens (light output) per watt. Thus, where space

allows, use four foot tubes. If there is not enough space for these, individual compactfluorescents may be called for.

Manufacturers

In North America the "Big Three" in fluorescent tube manufacturing are GeneralElectric (GE), Sylvania and Philips. They all make, almost without exception, the sametubes, under different trade names although there are some notable exceptions.Smaller and off-shore manufacturers include Duro-test in the US and Osram whomake some tubes in North America and some in Europe.

Industrial Tubes

These tubes include the ubiquitous "cool white" and "warm white" usually used inhome and industrial lighting applications. These tubes are tuned to produce thebrightest possible illumination for the least amount of electricity. Since the humaneye is most sensitive to green, these tubes peak in the green portion of the visiblespectrum. In fact they rise and fall quite sharply either side of the green peak. Warmwhite is shifted a bit toward the red end of the spectrum thus accounting for the"warmer" appearance.

If all you want to do is illuminate your plants these tubes are fine. These tubes arecheap, and they don't look terrible. Recent evidence suggests that although plantsrequire mostly red and blue light, ANY light, in high concentration must be applied forthe plants to open their stomata thus permitting respiration. This goes a long way

toward explaining why some people are able to grow beautiful plants with just coolwhite and warm white tubes. Enough light, of any type will grow plants. These tubesare far from optimal however and they really are almost completely devoid of thenecessary red and blue portion of the spectrum. If you can grow decent plants underthese lights, you will do even better under more appropriate lights. These tubes areavailable anywhere fluorescent tubes are sold and are the cheapest tubes available.

Daylight


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Daylight tubes are the next big improvement in more natural light (that is a morecloser approximation of sunlight) as a result of an improved phosphor formulation.Although daylight tubes output a spectrum that although does not fully emulatesunlight, it is significantly better than earlier cool white and warm white tubes. Thesetubes are occasionally available at hardware and department stores. They are notuncommon and any lighting supplier should have them or be able to order them.

They cost a bit more than cool white, but are not expensive. Figure about $3 to $4.

Plant Growth Lights

Epitomized by the Sylvania Gro-Lux tube, plant growth lights are, unlike all otherfluorescent tubes, meant solely for promoting plant growth; you won't find theseilluminating somebody's home or office - with one exception. Where I work, areceptionist thought it would be nice to have pink lighting in the lobby and orderedand had installed some plant growth tubes. You do get used to it, but they are mostdisconcerting when initially encountered.

GE's version of this tube is called "Gro-N-Sho". Gro-Lux type tubes have an outputspectrum with two large spikes, one in the blue, and one in the red portion of the

spectrum. There is almost no light emitted in any other portion of the spectrum andas such, they cast an eerie purplish glow and do not appear very bright. The spikes inthe red and blue occur quite abruptly and are quite steep. This spectrum was chosenas it matched the absorption of visible light by chlorophyll in a test tube. In the 50's astudy was conducted on various lighting types and phosphor formulations on plantgrowth, the results of which were published in the book "Lighting for Optimal PlantGrowth" (Kent State Press) The phosphor formulation of Gro-Lux type tubes wasimproved upon. Instead of two steep abrupt spikes in the red and blue, there are twoslow rising large "bumps"; the peaks in the red and blue were not as high, nor didthey rise as sharply. Instead of concentrating all the energy in these two narrowenergy bands, the output was tuned to produce wider bands still centered around redand blue. It became commercially available from Sylvania as Gro-Lux Wide Spectrum;GE named theirs Gro-N-Sho Wide Spectrum. These are more pinkish than purple and

are indeed what is in the lobby of the building where I work.

Incidentally, you could never get away with regular Gro-Lux (as opposed to Gro-Luxwide spectrum) tubes in a lobby; they look dark, don't illuminate well and are a verydeep purple. The Wide spectrum plant lights are brighter and don't look like a 60'spsychedelic poster shop when used to illuminate a room like a regular Gro-Lux would.

Philips makes a plant light they named "Agro-Lite", which is a minor variant of thewide spectrum Gro-Lux. They commissioned a study at a major American universitycomparing their Agro-Lite to wide spectrum plant lights. The Philips tube resulted in 2- 10% greater growth in a variety of terrestrial food crops when compared to otherwide spectrum plant lights.

Since these tubes are quite commonly used for houseplants they are reasonablycommon in hardware stores or nurseries, although what typically happens is a storewill only sell one vendor's fluorescent tubes. Even worse, they don't recognize thedifference between plant lights and wide spectrum plant lights with the result beingyou will usually find plant lights or wide spectrum plant lights from one manufacturerin a store. Wide spectrum tubes are reasonably inexpensive, although regular Gro-Lux type tubes tend to be a bit more expensive still - the chemical that makes up thephosphor which produces red is the expensive part. In a pet shop these can be


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between $10 and $20. From a lighting supplier a Gro-Lux tube is about $9 while awide spectrum tube is about $7.

Full Spectrum

Full spectrum tubes imitate natural sunlight as closely as possible by emitting light in

every spectral range. All the different colours of visible light and a very small amountof ultraviolet is emitted. The Duro-Test Company produces "Vita-Lite" tubes. GEproduces "Chroma 50", Philips produces "Colortone 50", Sylvania produces "Designer5000K". All these tubes have an output spectrum that is similar to sunlight - about asclose as modern chemistry can bring us. These tubes try to imitate equatorialsunlight at noon, which has a colour temperature of around 5000K.

Noon-day sunlight from northern climes has a larger amount of blue in the spectrum,having a colour temperature of 7500 Kelvin. Since the red pigment in plants is limitedby blue light, these are sometimes useful. Duro-Test sells a "Vita Lite 75", GE sells a"Chroma 75" and Philips sells a "Colortone 75".

There is quite a disparity in availability and price of these tubes. The Vita Lites have

very good distribution. They can be found in most aquarium stores (and many petstores as they are also used for illuminating lizards who need the Vitamin D from theultraviolet light). The downside of this is like anything you buy in a pet store that youcan buy in a hardware store, the price can be quite high when buying them from apet store: $15 - 20+. The same Vita-Lite tube from a lighting supplier is about $7,and the Chroma 75 I have obtained for less than $5. They are nearly identical.

Tri-Phosphor

Philips makes the most popular range of T12 tri-phosphor tubes, the "Ultralume"series. Recognizing that the primary light colours are red, green and blue, Philipsmade a tube that fluoresces very sharply only in these three narrow wavelengths.

The light emitted appears white, and very bright. They are used primarily in clothingstores because they completely lack emitted ultra-violet, which bleaches clothes.Ultralumes come in colour temperatures of 3000, 3500, 4000, 4500, and 5000 whichis accomplished by varying the amounts of red, green and blue phosphors. Since redis the most difficult colour light to obtain from fluorescent tubes and the Ultralume 35has the most red, this is probably the most interesting tube from our perspective.Ultralumes are in the $7 range and can be found at better pet/aquarium stores.Philips tubes seem to be difficult to find in some areas, notably the West coastalthough I have occasionally seen Ultralumes on sale in department stores there.Again, a lighting supplier can usually get any of these tubes.

Actinic

These tubes emit light only from the blue end of the spectrum and are used in marinesetups to supply the blue that is missing from normal aquarium lighting but isrequired by marine algae, anemones and corals. They are usually only available fromspecialty aquarium stores and are not cheap. They have little or no application forgrowing plants.

Reflector and Aperture


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Of the large manufacturers of fluorescent tubes, only Sylvania makes reflector andaperture tubes. Many of the new aquarium specific tubes have reflectors, but havelittle data to back up their assertion that the reflector is worth the extra cost.Sylvania however, has a data sheet on their reflector and aperture tubes.

Quoting from the "Sylvania Engineering Bulletin O-338"

"Aperture and reflector fluorescent lamps differ from standard fluorescent lamps inthat they allow a certain amount of control over the direction in which the light isbeing sent. As sketched in Figure 1, a reflective coating is placed between the outerglass and the phosphor coating. This reflective coating provides the direction controlby reflecting most of the incident light and directing it through the uncoated surfaceor clear window of the aperture lamp.

The total light output of reflector lamps is actually less than that of standard lamps.These lamps are intended for applications which can best utilize their special lightdistribution. The light is often too bright for direct illumination, but when used withreflectors it can be a very effective means of controlling the light."

Reflector tubes have a reflective coating covering 235 (or 135) degrees of theinterior. Over that they have a phosphor covering the entire inside of the bulb. Theyare available in a number of sizes in Cool White, while one is available in Gro-Lux in aR/GRO/VHO 215 Watt 96" lamp.

Aperture lamps have a 330 or 300 degree reflective coating. They have a phosphorcoating covering 330 or 300 degrees of the lamp. There is a 30 or 60 degree clearglass opening or "aperture".

The aperture lamp has a lower light output that standard fluorescent lamps, becausesome of the phosphor, which converts ultra violet to visible light, has been removed.But when these lamps are used with reflectors or lenses, they provide a very

concentrated beam closely projected in one direction. This allows more light to bedelivered to a small area.

"Applications of the lamp are bridge lighting from the rails, aircraft landing strips,highways and approach ramps, billboards and sign lighting, sport areas and marinalighting."

The aperture lamps are only available in 3 models: 4 foot 30 degree aperture coolwhite, 4 foot 60 degree cool white, and 8 foot HO 30 degree cool white.

HO/VHO

HO refers to High Output, and VHO is Very High Output. These tubes output more

(and a lot more) light by drawing more (and a lot more) current. They are moreexpensive tubes to buy, require larger more expensive ballasts and don't last as long.

The conventional wisdom about these tubes is that if you need a lot of light then it'sokay to use an HO, but the VHO's are more bother than they're worth. Neither last aslong as regular tubes. A ballast for an 8 foot VHO tube is an enormous black box thatdraws a lot of current, and gets very hot. Even the tubes themselves get hot. If youneed this much light you should probably be thinking about HID lamps. HO and VHOtubes come in many sizes and types, such as cool white, warm white, daylight, Gro-Lux and Gro-Lux wide spectrum


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Longevity

Standard T12 four foot fluorescent tubes have about a 10,000 hour lifespan, but asstated earlier, their usable life is much shorted because of decreased light outputover time. All other tubes are less (by about half) than this, but again, it's a mootpoint as they should be replaced every six months.

HID LAMPS

Now we're getting serious

HID or High Intensity Discharge are the big bright lamps you see in grocery stores,street lighting and industrial lighting. They can be very large and draw a lot of power.Indeed 2000 watt and 6000 watt lamps exist, however small ones, down to 70 wattsare available.

Tradeoffs

These lamps produce a lot of light output quite efficiently, however they can be quiteexpensive to install initially and may require a fan for cooling in the housing/reflectoras they can produce phenomenal amounts of heat. These lamps are used by growerswho need lots of light.

HID lamps requite a ballast, and almost every bulb requires it's own type of ballast.The ballasts are expensive and bulky and are not something you trot on down to thecorner hardware store to pick up, although larger hardware stores may have some;they are usually reasonably priced. You'll have to go to a lighting supplier for most ofthem however.

HID lamps are built like halogen bulbs. A small capsule contains the vapour that anarc is sent through. This capsule is in turn encased in the much larger outer bulb

body. There is quite a bit of UV generated by the inner capsule that is filtered by theouter capsule. All these bulbs carry warnings not to operate them if the outer capsuleis broken.

Types

There are three basic types of HID lamps: mercury vapour, sodium vapour and metalhalide.

Mercury vapour

When you see a bright light illuminating some industrial building and it has a decided

bluish cast - that's mercury vapour. Mercury vapour lamps have an output spectrumthat is almost entirely blue-white, with very little red. Worse, the spectrum is notcontinuous, there are spectral peaks at certain wavelengths. These lamps, althoughnot useless - there is no doubt very good results can be obtained with them - areequivalent to cool white fluorescents. Yes they work, but why bother going to thisexpense and trouble when other bulbs will yield much greater success?

One interesting variation on this theme is the self ballasted bulb. These bulbs(around 250 watts) require no ballast, they just screw into a standard medium base(ie. incandescent) fixture and voila, light. These lamps have a duo-spectrum for


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colors, besides it emitting light on the blue/white end of the spectrum, it does emitreddish/yellow light (from the filaments), therefore, it does have more of a lightspectrum that plants depend on. The downside is these bulbs are not as efficient asregular mercury vapour lamps because they use the resistive properties of the largefilaments as a ballast, and these bulbs are expensive, around $50 for 250 watts. Ofcourse with mercury vapour lamps having a 10,000 hour lifespan the high cost of the

bulb must be considered in view of the lack of expense for a ballast.

Sodium vapour lamps

These lamps come in two varieties, high pressure sodium and low pressure sodium,although this is rather a moot point, as the light they output is monochromatic (pure)yellow, and are generally used in conjunction with sunlight or metal halide lights.

They are a full ten times more efficient then incandescent bulbs, in fact these are themost efficient bulbs made, and have a 24,000+ hour lifespan. These are one of thecheapest HID bulbs to purchase, and can be found in most hardware stores foraround $80 for bulb and ballast. Spare bulbs are around $30.

Metal Halide

Like sodium vapour, these lamps come in two versions, regular and colour corrected(HQI) versions. The HQI versions have a uniform, sunlight-like output spectra,whereas the standard halide bulb has a lot of yellow, some blue and not much red.Unlike sodium vapour, these lamps are very useful to the grower needing a lot oflight. They can be found nominally in 250, 400, and 1000 watt sizes, from mostmanufacturers, but Osram also makes a 70 watt and a 150 watt size. The 70 wattbulb is only 2 x 3 inches, although is unfortunately a 3000K colour temperature bulb.

You have to go to a 250 watt bulb to get 5400K colour temperature.

These bulbs range in life from 6000 to 10,000 hours. Bulbs are around $50, ballastsare around $100.

Some sample setups

Obviously with a plethora of different type of lighting systems to choose from, tryingto figure out what tube to use can be a nightmare. Largely it depends on what youare trying to illuminate, and what your budget it. It also depends on what size areayou are trying to illuminate.

Many small plantstands have a small plastic or metal hood that has one or two tubeshaped incandescent bulbs. For the bulbs to provide enough light to grow plants theyneed to be of such high wattage that there can be an excessive amount of heat beinggiven off from the bulbs.

Incandescent illumination, although inexpensive in initial setup cost is notrecommended. The heat generated by these light bulbs almost always overheats theplants. The cost to operate is fairly high, and the quantity of light is low compared tothe amount of heat produced. Some of the smaller halogen bulbs are useful forsupplementing fluorescent lights, as the halogens, because they are stillincandescent, put out quite a bit of red light. Not only does this help to balance thespectrum, but it has a more pleasant aesthetic appearance.


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Theoretically a 300 or 500 watt halogen lamp could be used but 500 watts is a lot ofenergy; a 175 watt metal halide bulb will provide the same amount of light for a lotless energy. The only practical use for incandescent lights would be in a setup thatwas primarily fluorescent. A couple of small halogen bulbs, if well shielded from watersplashes would provide the red light so needed by plants.

Fluorescent lights are the most economical way of lighting your plants in the longrun. Once the initial purchase of the fixture is made the low cost of operation andlong life of the tubes makes fluorescent light very attractive. For a beginner that hasan incandescent fixture the new compact fluorescent bulbs with integrated ballastswill, in many cases, screw right into the existing socket. Bulbs for these are availablefrom 2700K to 5000K colour temperatures, although as of this writing only Osrammakes 5000K compact fluorescents.

The absolute cheapest setup is to buy whatever fluorescent tubes are on sale at thelocal hardware store. Usually cool white. This is far from the best, but it will work.One cool white and one warm white is a little better, although one plant growth lightand one daylight bulb is still a fairly cheap setup, (both are well under $10) with quitegood light quality.

For growing plants, a setup consisting of one plant light, two wide spectrum plantlights and one chroma 75 (or equivalent) will provide the right amount of the correcttype of light. Triton (or equivalent) tubes could be used of cost is no object. If thepinkish colour is objectionable, two Ultralume 3500 and two Ultralume 5000 can beused instead of the wide spectrum plant lights.

Low light plants will do ok under two Gro-Lux or Gro-Lux wide spectrum tubes.

For growing high light plants, two (or four, depending on preferences) chroma 75'scan be used. Or an HID lamp would probably be the most appropriate. Rather than alarge number of fluorescent tubes to supply enough light, it would have beencheaper to install a halide lamp in the first place.

The cost of the HID lamps is pretty large, and even worse, the more useful lamps togrowers of plants are even more expensive. Usually mercury vapour or sodiumvapour lamps are available at semi-reasonable rates from hardware stores wherethey are sold as security light; especially in rural areas. I have heard of people tryingsodium vapour lamps, but have never heard of any success with them. People havehad some mixed success with mercury vapour lamps. Metal halide lamps give verygood results, but are the most expensive and difficult to obtain of all the HID lamps.

For applications requiring a REALLY BRIGHT light, the current GE lighting catalog listsa 10,000 watt carbon arc lamp used for lighthouses.

Summary and conclusions

Like everything else in life you get what you pay for. Lighting systems can be builtfrom apple juice cans and incandescent fixtures for almost nothing, or the latest andgreatest in HID lighting can be ordered from Germany.

For most people, fluorescent light will be the reasonable compromise between costand quality of light. For a little bit of effort, the specialized fluorescent tubes can be


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sought out with only a little bit of time and a bit more money than the ubiquitous coolwhites hanging over the workbench.

ARTIFICIAL LIGHTING

A Summary of Artificial Illumination as it Pertains to the Culture of VarousPlants and Animals Commonly Kept in Indoor Aquaria

by Richard J. Sexton([email protected])

Document History | Scope of this Document | Copyright Notice |Introduction | Light and Color | Natural Sunlight | Incandescent Lighting |Fluorescent Lighting | HID Lamps (incl. MH) | Sample Setups | Summary andConclusion

DOCUMENT HISTORY:

May. 1989: WrittenNov. 1989: Major Revision, Posted to UseNet aquaria newsgroupsOct. 1991: Printed in Aquatic Gardners BulletinNov. 1992 Printed in Southern California Killi Club bulletinAug. 1995, Conversion to HTML by Erik OlsonNov.1995, Minor revisionsAug.1996: Published in Killi Dirt, bulletin of the Canadian Killifish

AssociationAug. 1998: Added "Related Reading" compiled by Stephan Boulet

Scope of This Document
mailto:[email protected]://www.geocities.com/CapeCanaveral/4742/lighting.html#histhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#scopehttp://www.geocities.com/CapeCanaveral/4742/lighting.html#coprhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#introhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#colorhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#sunhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#incandescenthttp://www.geocities.com/CapeCanaveral/4742/lighting.html#fluorescenthttp://www.geocities.com/CapeCanaveral/4742/lighting.html#hidhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#sampleshttp://www.geocities.com/CapeCanaveral/4742/lighting.html#summaryhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#summaryhttp://www.cco.caltech.edu/~aquaria/Krib/Authors/erik.htmlhttp://www.cka.org/http://www.cka.org/mailto:[email protected]://www.geocities.com/CapeCanaveral/4742/lighting.html#histhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#scopehttp://www.geocities.com/CapeCanaveral/4742/lighting.html#coprhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#introhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#colorhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#sunhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#incandescenthttp://www.geocities.com/CapeCanaveral/4742/lighting.html#fluorescenthttp://www.geocities.com/CapeCanaveral/4742/lighting.html#hidhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#sampleshttp://www.geocities.com/CapeCanaveral/4742/lighting.html#summaryhttp://www.geocities.com/CapeCanaveral/4742/lighting.html#summaryhttp://www.cco.caltech.edu/~aquaria/Krib/Authors/erik.htmlhttp://www.cka.org/http://www.cka.org/


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While mostly aimed at aquarists, this article is also applicable to other peopleinterested in growing things under artificial light.

Copyright Notice

Copyright 1995 Richard J. Sexton

Freedom to distribute this article in cyberspace for non commercial purposes isgranted by the authors, providing attribution is given. All other uses, contact theauthor.

Introduction

There are a number of different approaches used for illuminating aquaria. To makean informed decision as to what type of lighting should be employed, thefundamentals of light, color and lighting systems should be understood. In this articlewe will examine the how light is qualitatively appraised with respect to color andintensity. Different lighting systems will be examined, and most available types oflights will be discussed. Examples of some "real world" lighting systems will be givenand analyzed with respect to effectiveness, initial cost, operating expense andlongevity.

LIGHT AND COLOR

What is light?

Visible light is that part of the electro-magnetic spectrum that lies between thewavelengths of ultraviolet and infrared. That's probably more that you need to knowfor the purposes of home aquaria.

White light is all colors

When we see a rainbow, we are seeing white light split up into it's component colors,hence the expression "all the colors of the rainbow".

Sunlight is different in different places in the world

Sunlight contains, more or less, equal portions of all colors of sunlight. Northernsunlight, that is, sunlight in areas north of the fortieth parallel, has more blue thanequatorial sunlight because of absorption of all other colors, or wavelengths of light,by the atmosphere.

Blue pictures underwater

This is the same effect that causes underwater photos taken below three feet to beso blue. Just as the atmosphere absorbs non-blue light so does water, except waterabsorbs non-blue light at a much greater rate. Almost all non-blue light below threefeet of water is absorbed.

How is light measured?


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Light quality is expressed and measured in many ways. Light color can be measuredin degrees Kelvin (K) and the color rendering index of a light source can be measuredand expressed as CRI.

Color temperature - degrees K

White light can have different "warmth". A bit more red/yellow and white lightappears "warmer". A bit more blue and light appears "cool". This can bequantitatively assessed by the assigning of a color temperature, given in degreesKelvin. Think of color temperature as the color of a block or iron as it is heated tovarious high temperatures. A warm, reddish light is around 3500 degrees Kelvin, andabove 6000 degrees Kelvin the light takes on a bluish tone. Sunlight is somewherearound 5000 degrees Kelvin. The first part of the paragraph is misleading. Althoughpeople may think of blue as a "cooler" color than red, it is actually hotter. For thephysicists out there, iron is acting as a black body here.

Color rendering index (CRI)

The color rendering index identifies the degree of color shift objects undergo when

illuminated by a particular light source. In simpler terms, the CRI expresses thedegree to which a light source renders the true color impression. The CRI is an indexand ranges from 0 to 100. A light source having a CRI of 100 means objectsilluminated by it look like they're supposed to; that is their natural color is notdistorted. A light source having a very low CRI would tend to make objects appear tobe a different shade or even color that they really are. An example of light with ahigh CRI is, obviously, sunlight. Some fluorescent tubes such as Daylight, Chroma 65or Vita-Lite have a very high CRI. Some light sources such as Gro-Lux or sodiumvapor lamps have very low CRI's.

NATURAL SUNLIGHT

Good light, free, but hard to control

This is of course what fish and plants are used to, and it can hardly be argued thatthis is anything less than the most natural. However, coaxing enough sunlight intoyour aquarium, from the top, rather than through the sides, throughout the wholeyear, can be problematical.

Sunlight is the certainly the cheapest way to illuminate an aquarium, although it isunreliable and very difficult to regulate. This, of course is subject to geographicalvariation. If you live in California and have a skylight over an aquarium, you might begetting enough light. If however, you live in an area that does not get a lot ofsunlight, and your aquaria are stacked in rows in a basement you will obviously needsupplemental lighting.

Very few people use sunlight as a primary lighting source, although it is often used assupplemental lighting. Scrutinizing the photos of the 10,000 liter Dupla tank in theHorst and Kipper book _The Optimum Aquarium_ you may notice that besides havinga number of powerful Metal Halide lamps there are skylights for auxiliary lighting.

INCANDESCENT LIGHTING

Cheap, low quality light


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Incandescent lights are the ubiquitous screw-in bulbs you most likely have lightingyour home. An Incandescent bulb consists of a glass bulb, with a tungsten filament ina near vacuum; just a small amount of argon or krypton is present. When currentflows through the filament it heats up, and glows giving off both heat and light.

Halogen bulbs

A variation of the incandescent bulb is the halogen bulb. This is an improvement toincandescent bulbs invented by GE in 1958 for the wing tip navigation lights of theBoeing 707. In a regular incandescent bulb, the tungsten filament evaporates, andover time the inside of the bulb is coated with a fine coat of tungsten from condensedtungsten vapor. This coating will severely limit the light output of the bulb. In ahalogen bulb, a small amount of one of the halogens (Iodine or Bromine are used) ispresent and combines with the evaporated tungsten. This Tungsten Iodide or

Tungsten Bromide molecule has an affinity for the tungsten filament, and returnsthere and splits. The tungsten from this molecule returns to the filament while thehalogen returns to the atmosphere inside the bulb. This process does not work unlessthe bulb jacket is at least 200 degrees Celsius. This is why halogen lamps are so hot,and must be taken into consideration for aquarium applications. Halogen lamps are

25-30% brighter than regular incandescent bulbs. The halogen cycle, as it is called,takes place in a very small capsule, as it is easier to maintain the high temperaturerequired for the halogen cycle to operate in a smaller space. This capsule is placedinside another glass capsule which serves as the bulbs outer casing and although isstill plenty hot, is not as hot as 200 degrees Celsius.

Output spectra is biased towards the red

The output spectrum of incandescent light, halogen or regular, is biased heavilytoward the red. Non halogen bulbs have a color temperature of 2700K, while halogenbulbs have a color temperature of 3000K - they are a slightly more whitish light. Bothhave a CRI of 100. A diagram of the spectra looks rather like a triangle, starting withalmost no output in the green and rising at an almost linear rate to the far red and

infra red. Although incandescent bulbs are very inefficient, they are a very goodsource of near and far red light which is certainly very important. They aresometimes used as supplements in systems which are deficient in the red end of thespectra.

Efficiency

The two great disadvantages to incandescent lights are their inefficiency - you don'tget a lot of light compared with how much energy you put apply. One saving grace inthis respect is that the efficiency increases proportionally to the wattage, for examplea single 100 watt bulb is much brighter than two 50 watt bulbs. The energy that doesnot get converted to light is wasted by being given off as heat. All but the smallestwattage bulbs can generate an awful lot of heat, and this must be taken intoconsideration. Another point to consider is, because the heat is so great, a splash ofwater on a hot bulb can shatter it.

Halogen bulbs are more efficient than "regular" incandescent bulbs by virtue ofremaining brighter, longer; they still give off 95% of their initial light output at theend of their lives, which are about twice as long as regular incandescent bulbs. Theyare also more expensive.


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The great advantage of non halogen bulbs is of course their extreme low cost forinitial purchase, and of course their great availability; you can buy them anywhere.Halogen bulbs are on the average 5 to 10 times as expensive as their non halogencounterparts and can usually be found at larger hardware stores. Since their primarymarket is yuppie track lighting they are usually found as spot or flood lights. Ofpotential interest to aquarist is the low voltage bulbs used in some track lighting

systems. Operating as 12V, these bulbs are quite small and would be good to use asupplemental light augmenting a fluorescent setup. They are also the cheapest ofhalogen bulbs. While I have seen them at $30 each in fancy designer light stores, Ihave also seen them in Price Club at 3 for $12. Sylvania makes a series of bulbscalled Capsylite that come in "regular" bulb shapes plus the large parabolic reflectorssometimes used to illuminate the outside of houses. Osram makes a large array ofdifferent shapes and sizes, most of which look like the vacuum tubes. They areprobably the most useful to aquarists because of their smaller size and wide range ofwattages; from low power bulbs all the way up to 150 watts. They are however notcheap and can be quite a challenge to find somewhere that stocks them.

Longevity

Incandescent bulbs have a lifespan of about 1000 hours. Halogen bulbs have a life ofabout 2000 hours. One interesting personal note here; although regular incandescentlights are rated at 1000 hours, we've all had some bulbs that seem to burn onforever. The Guiness book of world records lists the longest lasting light bulb as beingan incandescent bulb in a fire house in, I believe Boston that is some 70+ years old;it is never turned off, which is a key point. This is why your parents always gave youhell for flicking the lights on and off really quickly, the wear on the filament fromhaving current suddenly shot through it is quite great. If you'll notice, most bulbs failwhen turned on, not in the middle of operation, or when they are turned off. Thehalogen bulbs I have throughout my home seem to be on a timer; when 2000 hoursis up *poof*, they expire. I curse them out, do a rough calculation and come to theconclusion that their 2000 hours just expired.

FLUORESCENT LIGHTING

Cheaper To Run, More Expensive To Install

Fluorescent lights are very common in our day to day lives. They are cheap tooperate as they emit about four times as much light per unit of electricity asincandescent lights do. On the other hand they are more complicated to installbecause they require a ballast to operate. You may be familiar with the regular "coolwhite" and "warm white" tubes sold in hardware stores but what you may not know isthat fluorescent tubes come in hundreds of shapes, sizes and spectral output.

How They Work

Fluorescent lights work by placing an anode and a cathode at opposite ends of aglass tube. Inside the tube is a partial vacuum and a small amount of mercury vapor.When energized, the mercury vapor is ionized and emits ultraviolet radiation. Theinside of the tube is coated with a phosphor - a powder that "fluoresces" (gives offlight) when stimulated by ultraviolet radiation, thus producing visible light. Thechemical composition of the phosphor determines the spectra or color of the emittedlight.

Replace Tubes Every Six Months


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Although fluorescent lights are very energy efficient, there is a particularly nastyphenomenon known as "cathode decay" that causes, over time, less energy to betransferred through the mercury vapor. The net effect is that the tube will emit lessand less light as it gets older. To all appearances, the tube will put out the sameamount of light until it suddenly stops dead one day, (which can take years), but forall practical purposes, because the drop off in light output is an exponential decay,

the tube should optimally be replaced every six months or at the very least once ayear. Writing the installation date on the tube itself with a permanent magic markercan be a big help here.

Types Of Fluorescent Tubes

There are many different types of fluorescent tubes. They differ in the physical size,composition of the phosphor and the wattage. When fluorescent tube is mentionedthe standard T12 four foot tubes usually comes to mind. This tube has a diameter of1.5 inches and is available in 18", 24" 36", 48", 72" and 96" lengths. The T8 or"slimline" fluorescent has a 1" diameter tube and is available in 24", 36" and 48"lengths. T12 tubes are also available in U-shaped, that is a four foot tube is bent backon itself so it forms a large U, and is about 24" long. Circular tubes are available with

several different radii, and in several different types. In the last few years, compactfluorescent tubes have become very popular mostly as replacements forincandescent bulbs. These tubes come in all sizes, from a 3" 5 watt bulb to muchlarger bulbs that replace 40W four foot tubes, yet are just one third of the size. Thephosphor chemistry is what makes the difference between a cool white and adaylight tube and every tubes is available with a dizzying array of choices in thisarea. Some of the most useful tubes for aquarists with small tanks are the 5000Kcompact fluorescent tubes. T12 tubes are available in HO (High Output) or VHO (VeryHigh Output) which draw more and much more current respectively, but producemore light than regular T12 tubes. As the composition of the phosphor changes sodoes the spectra of the visible light being emitted by the tube. For aquarium use,whether for illumination for plant growth or to simply be able to see inside the tankonly a small percentage of the dozens of available tubes are appropriate. They fall

into the following broad categories: industrial, full spectrum, daylight, plant growth,actinic, tri-phosphor, special purpose and HO/VHO.

Use Four Foot Tubes

Although fluorescent tubes come in many sizes, volume of scale dictates that there isreally only one size - the T12 four foot length. Some ninety percent of all fluorescenttubes made are this size, and because of this volume, this is the cheapest size,although this needs to be qualified. If you are buying tubes through normal retailchannels, the markup is generally high enough that they can play with prices and a24 inch tube costs less than a 48 inch tube but more than an 18 inch tube. If howeveryou are buying tubes through other channels, such as lighting distributors, you mayfind that the four foot tube is cheaper than any other size. T12 tubes that are smaller

or larger will cost you more. Additionally, the four foot size has the longest lifespanand also the highest ratio of lumens (light output) per watt. Thus, where spaceallows, use four foot tubes. If there is not enough space for these, individual compactfluorescents may be called for.

Manufacturers

In North America the "Big Three" in fluorescent tube manufacturing are GeneralElectric (GE), Sylvania and Philips. They all make, almost without exception, the same


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tubes, under different trade names although there are some notable exceptions.Smaller and off-shore manufacturers include Duro-test in the US and Osram whomake some tubes in North America and some in Europe. There are a small number ofspecialty tube manufacturers aimed specifically at the hobbyist aquarium market.

Industrial Tubes

These tubes include the ubiquitous "cool white" and "warm white" usually used inhome and industrial lighting applications. These tubes are tuned to produce thebrightest possible illumination for the least amount of electricity. Since the humaneye is most sensitive to green, these tubes peak in the green portion of the visiblespectrum. In fact they rise and fall quite sharply either side of the green peak. Warmwhite is shifted a bit toward the red end of the spectrum thus accounting for the"warmer" appearance.

If all you want to do is illuminate your tank these tubes are fine. These tubes arecheap, and they don't look terrible. Recent evidence suggests that although plantsrequire mostly red and blue light, ANY light, in high concentration must be applied forthe plants to open their stomata thus permitting respiration. This goes a long way

toward explaining why some people are able to grow beautiful aquarium plants withjust cool white and warm white tubes. Enough light, of any type will grow plants.These tubes are far from optimal however and they really are almost completelydevoid of the necessary red and blue portion of the spectrum. If you can grow decentplants under these lights, you will do even better under more appropriate lights.

These tubes are available anywhere fluorescent tubes are sold and are the cheapesttubes available, figure in 1990 US dollars these tubes cost between $1 and $2.

Daylight

Daylight tubes are the next big improvement in more natural, (that is a more closerapproximation of sunlight) fluorescent tubes as a result of an improved phosphorformulation. Although daylight tubes output a spectra that although does not fullyemulate sunlight, it is significantly better than earlier cool white and warm whitetubes. These tubes are occasionally available at hardware and department stores.

They are not uncommon and any lighting supplier should have them or be able toorder them. They cost a bit more than cool white, but are not expensive. Figure about$3 to $4.

Plant Growth Lights

Epitomized by the Sylvania Gro-Lux (tm) tube, plant growth lights are, unlike all otherfluorescent tubes, meant solely for promoting plant growth; you won't find theseilluminating somebody's home or office - with one exception. Where I work, areceptionist thought it would be nice to have pink lighting in the lobby and ordered

and had installed some plant growth tubes. You do get used to it, but they are mostdisconcerting when initially encountered.

GE's version of this tube is called "Gro-N-Sho", other plant growth tubes that areavailable are these tubes relabelled for specialty pet/aquarium companies. Gro-Luxtype tubes have an output spectra with two large spikes. One in the blue, and one inthe red portion of the spectra. There is almost no light emitted in any other portion ofthe spectra and as such, they cast an eerie purplish glow, and do not appear verybright. The spikes in the red and blue occur quite abruptly and are quite steep. Thisspectra was chosen as it matched the absorption of visible light by chlorophyll in a


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test tube. In the 50's a study was conducted on various lighting types and phosphorformulation on plant growth, the results of which were published in the book"Lighting for Optimal Plant Growth" (Kent State Press) The phosphor formulation ofGro-Lux type tubes was improved upon. Instead of two steep abrupt spikes in the redand blue, there are two slow rising large "bumps"; the peaks in the red and blue werenot as high, nor did they rise as sharply. Instead of concentrating all the energy in

these two narrow energy bands, the output was tuned to a wider output spectra stillhowever, centered around red and blue. It became commercially available fromSylvania as Gro-Lux Wide Spectrum; GE named theirs Gro-N-Sho Wide Spectrum.

These are more pinkish than purple and are indeed what is in the lobby of thebuilding where I work.

Incidentally, you could never get away with regular Gro-Lux (as opposed to Gro-Luxwide spectrum) tubes in a lobby; they look dark, don't illuminate well and are a verydeep purple. The Wide spectrum plant lights are brighter and don't look like a 60'spsychedelic poster shop when used to illuminate a room like a regular Gro-Lux would.

Philips makes a plant light they named "Agro-Lite", which is a minor variant of thewide spectrum Gro-Lux. They commissioned a study at a major American university

comparing their Agro-Lite to wide spectrum plant lights. The Philips tube resulted in 2- 10% greater growth in a variety of terrestrial food crops when compared to otherwide spectrum plant lights.

Since these tubes are quite commonly used for (non aquatic) houseplants they arereasonably common in hardware stores or nurseries, although what typically happensis a store will only sell one vendors fluorescent tubes. Even worse, they don'trecognize the difference between plant lights and wide spectrum plant lights with theresult being you will usually find plant lights or wide spectrum plant lights from onemanufacturer in a store. Wide spectrum tubes are reasonably inexpensive, althoughregular Gro-Lux type tubes tend to be a bit more expensive still - the chemical thatmakes up the phosphor which produces red is the expensive part. In a pet shop thesecan be between $10 and $20. From a lighting supplier a Gro-Lux tube is about $9

while a wide spectrum tube is about $7.

Full Spectrum

Full spectrum tubes imitate, as closely as possible, natural sunlight by emitting lightin every spectral range. All the different colors of visible light and a very smallamount of ultraviolet is emitted. The Duro-Test Company produces "Vita-Lite" tubes.GE produces "Chroma 50", Philips produces "Colortone 50", Sylvania produces"Designer 5000K". All these tubes have an output spectrum that is similar to sunlight- about as close as modern chemistry can bring us. These tubes try to imitateequatorial sunlight at noon, which has a color temperature of around 5000K.

Noonday sunlight from northern climes has a larger amount of blue in the spectrum,as has a color temperature of 7500 Kelvin. Since the red pigment in plants is limitedby blue light these are sometimes useful. Duro- Test sells a "Vita Lite 75", GE sells a"Chroma 75" and Philips sells a "Colortone 75".

There is quite a disparity in availability and price of these tubes. The Vita Lites havevery good distribution. They can be found in most aquarium stores (and many petstores as they are also used for illuminating lizards who need the Vitamin D from theultraviolet light). The downside of this is like anything you buy in a pet store that youcan buy in a hardware store, they price can be quite high when buying them from a


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pet store: $15 - 20+. The same Vita-Lite tube from a lighting supplier is about $7,and the Chroma 75 I have obtained for less than $5. They are nearly identical.

Tri-Phosphor

Philips makes the most popular range of T12 tri-phosphor tubes, the "Ultralume"

series. Recognizing that the primary light colors are red, green and blue, Philipsmade a tube that fluoresces very sharply only in these three narrow wavelengths.

The light emitted appears white, and very bright. They are used primarily in clothingstores because they completely lack emitted ultra-violet, which bleaches clothes.Ultralumes come in color temperatures of 3000, 3500, 4000, 4500, and 5000 which isaccomplished by varying the amounts of red, green and blue phosphors. Since red isthe most difficult color light to obtain from fluorescent tubes and the Ultralume 35has the most red, this is probably the most interesting tube from our perspective.Ultralumes are in the $7 range and can be found at better pet/aquarium stores.Philips tubes seem to be difficult to find in some areas, notably the West coastalthough I have occasionally seen Ultralumes on sale in department stores there.Again, a lighting supplier can usually get any of these tubes.

Actinic

These tubes emit light only from the blue end of the spectrum and are used in marinesetups to supply the blue that is missing from normal aquarium lighting but isrequired by marine algae, anemones and corals. They are usually only available fromspecialty aquarium stores and are not cheap. They have little or no application forgrowing freshwater aquarium plants.

Reflector and Aperture

Of the large manufacturers of fluorescent tubes, only Sylvania makes reflector andaperture tubes. Many of the new aquarium specific tubes have reflectors, but have

little data to back up their assertion that the reflector is worth the extra cost.Sylvania however, has a data sheet on their reflector and aperture tubes.

Quoting from the "Sylvania Engineering Bulletin O-338"

"Aperture and reflector fluorescent lamps differ from standard fluorescent lamps inthat they allow a certain amount of control over the direction in which the light isbeing sent. As sketched in Figure 1, a reflective coating is placed between the outerglass and the phosphor coating. This reflective coating provides the direction controlby reflecting most of the incident light and directing it through the uncoated surfaceor clear window of the aperture lamp."

"The total light output of reflector lamps is actually less than that of standard lamps.

These lamps are intended for applications which can best utilize their special lightdistribution. The light is often too bright for direct illumination, but when used withreflectors it can be a very effective means of controlling the light."

Reflector tubes have a reflective coating covering 235 (or 135) degrees of theinterior. Over that, they have a phosphor covering the entire inside of the bulb.

Reflector lamps are available with a 235 degree or 135 degree internal reflector.


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They are available in a number of sizes in Cool White, while one is available in Gro-Lux in a R/GRO/VHO 215 Watt 96" lamp.

Aperture lamps have a 330 or 300 degree reflective coating. They have a phosphorcoating covering 330 or 300 degrees of the lamp. There is a 30 or 60 degree clearglass opening or "aperture".

"The aperture lamp has a lower light output that standard fluorescent lamps,because some of the phosphor, which converts ultra violet to visible light, has beenremoved. But when these lamps are used with reflectors or lenses, they provide avery concentrated beam, closely projected in one direction. This allows more light tobe delivered to a small area.

"Applications of the lamp are bridge lighting from the rails, aircraft landing strips,highways and approach ramps, billboards and sign lighting, sport areas and marinalighting."

The aperture lamps are only available in 3 models: 4 foot 30 degree aperture coolwhite, 4 foot 60 degree cool white, and 8 foot HO 30 degree cool white.

Special Purpose

Beginning in 1990, specialty aquarium supply companies began selling fluorescenttubes aimed specifically for the aquarium market. These tubes are sold primarily forthe marine trade, as corals and anemones have even more exacting requirementsthan freshwater aquarium plants. The first to be introduced was the Triton tube madeby Thorn/EMI for Interpet (who were in turn bought by GE in 1990) tube fromEngland. These are essentially a tri-phosphor design but give off a pinkish lightreminiscent of wide spectrum plant lights. The output spectra looks like a Gro-Luxwith an additional green spike. The amount of light they give off is quite substantial -but so is the price. They start in the $15-$20 range and go up. Essentially a "super

Gro-Lux" the Triton tube was significant in that it was the first fluorescent tubedesigned specifically for aquarium use. It is also significant in another respect. Themanufacturer claims the spectral output of the tube degrades less than 10% over7000 hours, a time period in which a Gro-Lux type tube will have lost about 60 % ofit's light output. Also, unlike a regular fluorescent tube, a triton will just refuse to startor light up when it's life has expired (about 2 years). These features are meant toaddress the cathode decay problem and eliminate the need to change tubes.

It did not take long, however until other small manufacturers jumped on the specialtyfluorescent tube bandwagon. Looking at the January 1991 Freshwater and MarineAquarium magazine, there are no less than 5 different specialty fluorescent tubesadvertised. There is the "Actinic Day" tube which is a white tube with a fair amount ofactinic (blue, in the range of 380 - 480 nanometres) light as well. An ad for the Actinic

Day tubes compares the graph of their spectral output to that of the Triton tube, withnaturally, the actinic day tube showing a more intense spectrum. A few pages later isan ad for "Tritinic" brand tubes that are similar in design - tri-phosphor white with agood deal of actinic thrown in, and lo and behold is a graph comparing them toActinic Day tubes, with of course the Tritinic tube having a yet more intense outputspectra. Competition for your fluorescent tube dollar is fierce; it's a bloodbath outthere.

The superwhite/actinic tubes have a built in 180 degree reflector, which is simply apiece of metal insides the tube that covers the top of the tube so that all the light


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escapes directly out from the bottom half of the tube. This is not a new trick, someindustrial tubes (such as 8 foot VHO Gro-Lux) do this, but this is first tube for homeuse to employ such a device.

These tubes are made in small quantities for aquarium hobbyists and pricedaccordingly. They are only available from aquarium retailers and each cost $15+.

There is a specialty tube that is not a recent introduction nor is it made for homeaquaria. Sylvania makes a "fluorescent incandescent" that emits light much as anincandescent bulb does - mostly red and near red. They are almost never stocked,and are not cheap, about $10 US.

HO/VHO

HO refers to High Output, and VHO is Very High Output. These tubes output more(and a lot more) light by drawing more (and a lot more) current. They are moreexpensive tubes to buy, require larger more expensive ballasts and don't last as long.

The conventional wisdom in the aquarium trade about these tubes is that if you needa lot of light then it's okay to use an HO, but the VHO's are more bother than they're

worth. Neither last as long as regular tubes. A ballast for an 8 foot VHO tube is anenormous black box that draws a lot of current, and gets very hot. Even the tubesthemselves get hot. If you need this much light you should probably be thinkingabout HID lamps. HO and VHO tubes come in many sizes and types, such as coolwhite, warm white, daylight, Gro-Lux and Gro-Lux wide spectrum

Longevity

Standard T12 four foot fluorescent tubes have about a 10,000 hour lifespan, but asstated earlier, their usable life is much shorted because of decreased light outputover time. All other tubes are less (by about half) than this, but again, it's a mootpoint as they should be replaced every six months.

HID LAMPS

Now we're getting serious

HID or High Intensity Discharge are the big bright lamps you see in grocery stores,street lighting and industrial lighting. They can be very large and draw a lot of power.Indeed 2000 watt and 6000 watt lamps exist, however small ones, down to 70 wattsare available.

Tradeoffs

These lamps produce a lot of light output quite efficiently, however they can be quiteexpensive to install initially and may require a fan for cooling in the housing/reflectoras they can produce phenomenal amounts of heat. These lamps are used byaquarists who need lots of light, such as marine reef tanks, of large freshwater planttanks.

HID lamps requite a ballast, and almost every bulb requires it's own type of ballast.The ballasts are expensive and bulky and are not something you trot on down to thecorner hardware store to pick up, although larger hardware stores may have some;


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they are usually reasonably priced. You'll have to go to a lighting supplier for most ofthem however.

HID lamps are built like halogen bulbs. A small capsule contains the vapor that an arcis sent through. This capsule is in turn encased in the much larger outer bulb body.

There is quite a bit of UV generated by the inner capsule that is filtered by the outer

capsule. All these bulbs carry warnings not to operate them if the outer capsule isbroken.

Types

There are three basic types of HID lamps: mercury vapor, sodium vapor and metalhalide.

Mercury vapor

When you see a bright light illuminating some industrial building and it has a decidedbluish cast - that's mercury vapor. Mercury vapor lamps have an output spectra thatis almost entirely blue-white, with very little red. Worse, the spectra is notcontinuous, there are spectral peaks at certain wavelengths. These lamps, althoughnot useless - there is no doubt very good results can be obtained with them - areequivalent to cool white fluorescents. Yes they work, but why bother going to thisexpense and trouble when other bulbs will yield much greater success?

One interesting variation on this theme is the self ballasted bulb. These bulbs(around 250 watts) require no ballast, they just screw into a standard medium base(ie. incandescent) fixture and voila, light. The downside is these bulbs are not asefficient as regular mercury vapor lamps because they use the resistive properties ofthe large filaments as a ballast, and worse of all these bulbs are very expensive,around $100 plus or minus $30. Of course with mercury vapor lamps having a 10,000hour lifespan the high cost of the bulb must be considered in view of the lack of

expense for a ballast.

Sodium vapor lamps

These lamps come in two varieties, high pressure sodium and low pressure sodium,although this is rather a moot point, as the light they output is monochromatic (pure)yellow, and is all but useless in terms of aquaria. It's rather a shame, as they are afull ten times more efficient then incandescent bulbs, in fact these are the mostefficient bulbs made, and have a 24,000+ hour lifespan. These are one of thecheapest HID bulbs to purchase, and can be found in most hardware stores foraround $80 for bulb and ballast. Spare bulbs are around $30. Recent advances inhigh pressure sodium bulbs such as the Philips "Sun Agro" have improved outputspectra, and are quite popular for terrestrial plants, although they haven't as yet

gained great acceptance with aquatic gardeners.

Metal Halide

Like sodium vapor, these lamps come in two versions, regular and color corrected(HQI) versions. The HQI versions have a uniform, sunlight like output spectra,whereas the standard halide bulb has a lot of yellow, some blue and not much red.Unlike sodium vapor, these lamps are very useful to the aquarist needing a lot oflight. They can be found nominally in 250, 400, and 1000 watt sizes, from most


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manufacturers, but Osram also makes a 70 watt and a 150 watt size. The 70 wattbulb is only 2 x 3 inches, although is unfortunately a 3000K color temperature bulb.

You have to go to a 250 watt bulb to get 5400K color temperature.

These bulbs range in life from 6000 to 10,000 hours. Bulbs are around $50, ballastsare around $100.

Some sample setups

Obviously with a plethora of different type of lighting systems to choose from, tryingto figure out what tube to use can be a nightmare. Largely it depends on what youare trying to illuminate, and what your budget it.

It also depends on what size tank you are trying to illuminate, not so much as surfacearea or footprint of the tank, but depth of the water. The example setups below arefor four 15 gallon tanks turned sideways so that a four foot fixture across the top willilluminate all of them. Double the amount of light for deep tanks greater than 18inches.

Many small aquariums have a small plastic or metal hood that has one or two tubeshaped incandescent bulbs. For the bulbs to provide enough light to grow plants theyneed to be of such high wattage that there will be a severe and deleterious effect ofthe fish by the massive amount of heat being given off from the bulbs.

Incandescent illumination, although inexpensive in initial setup cost is notrecommended for aquaria. The heat generated by these light bulbs almost alwaysadversely affects the temperature stability of an aquarium. The cost to operate isfairly high, and the quality of light is poor compared to every other lighting system.Having said that I have seen some setups using incandescent lights that worked well.Plants were healthy, the tanks were not that hot. Be that as it may, if you get goodresults with incandescent lights you will get better results with fluorescents. Some of

the smaller halogen bulbs are useful for supplementing fluorescent lights, as thehalogens, because they are still incandescent, put out quite a bit of red light. Notonly does this help to balance the spectrum, but it has a more pleasant estheticappearance.

Theoretically a 300 or 500 watt halogen lamp can be suspended a foot above thetank, and this would provide enough light without cooking the fish, but 500 watts is alot of energy; a 175 watt metal halide bulb will provide the same amount of light for alot less energy. The only practical use for incandescent lights would be in a setupthat was primarily fluorescent. A couple of small halogen bulbs, if well shielded fromwater splashes would provide the red light so needed by plants.

Fluorescent lights are the most economical way of lighting an aquarium in the long

run. Once the initial purchase of the fixture is made the low cost of operation andlong life of the tubes makes fluorescent light very attractive. For a beginner tank thathas an incandescent fixture the new compact fluorescent bulbs with integratedballasts will, in many cases, screw right into the existing incandescent ballast. Bulbsfor these are available from 2700K to 5000K color temperatures, although as of thiswriting only Osram makes 5000K compact fluorescents.

The absolute cheapest setup is to buy whatever fluorescent tubes are on sale at thelocal hardware store. Usually cool white. This is far from the best, but it will work.


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One cool white and one warm white is a little better, although one plant growth lightand one daylight bulb is still a fairly cheap setup, (both are well under $10) with quitegood light quality. For growing plants, a setup consisting of one plant light, two widespectrum plant lights and one chroma 75 (or equivalent) will provide the rightamount of the correct type of light. Triton (or equivalent) tubes could be used of costis no object. If the pinkish color is objectionable, two Ultralume 3500 and two

Ultralume 5000 can be used instead of the wide spectrum plant lights.

For keeping African Cichlids, or any other fish that is used to a lot of light, two (orfour, depending on preferences) chroma 75's can be used.

Low light fish such a killifish and dwarf Cichlids will do best under two Gro-Lux or ifthey have an abundance of plant cover, two Gro-Lux wide spectrum tubes. Thesetubes will not frighten the fish with a lot of light, and they should encourage goodplant growth to provide much needed cover from the light. As an aside, I have keptcertain killifish such as Aphyosemion australe, A. gardneri, and A. sjoestedti underthe setup described above for plant growth and they didn't seem to mind. Somespecies of fish do not like a lot of light and in the wild will hide under cover to avoidintense light. In an aquarium with bright light and without some cover to take refuge

they will be as stressed as if they were forced in the wild from their shady environ toan area on bright light.

Marine invertebrates and certain freshwater plants have very large lightrequirements, and for these, an HID lamp would probably be the most appropriate. Itis unlikely you could put enough fluorescent tubes on top of the tank to supplyenough light, or if you could you may have spent so much on VHO lamps and ballaststhat it would have been cheaper to install a halide lamp in the first place.

The cost of the HID lamps is pretty large, and even worse, the more useful lamps togrowers of plants are even more expensive. Usually mercury vapor or sodium vaporlamps are available at semi- reasonable rates from hardware stores where they aresold as security light; especially in rural areas. I have heard of people trying sodium

vapor lamps, but have never heard of any success with them. People have had somemixed success with mercury vapor lamps. Metal halide lamps give very good results,but are the most expensive and difficult to obtain of all the HID lamps.

For applications requiring a REALLY BRIGHT light, the current GE lighting catalog listsa 10,000 watt carbon arc lamp used for lighthouses.

Summary and conclusions

Like everything else in life you get what you pay for. Lighting systems can be builtfrom apple juice cans and incandescent fixtures for almost nothing, or the latest andgreatest in aquarium HID lighting can be ordered from Germany.

For most people, fluorescent light will be the reasonable compromise between costand quality of light. For a little bit of effort, the specialized fluorescent tubes can besought out with only a little bit of time and a bit more money than the ubiquitous coolwhites hanging over the workbench.

Related reading


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Philips Lighting North America - The Light Sitehttp://www.lighting.philips.com/nam/

GE 4-Foot T8 Lamps with Starcoathttp://www.ge.com/lighting/business/products/starcoab.htm

Fluorescent Lamp Replacementshttp://www.ge.com/lighting/business/products/spspx.htm

OSRAM SYLVANIA Products - Reduced Mercury OCTRON T8 Lampshttp://www.sylvania.com/ic/products/t8.htm

Aquatic Plants FAQhttp://www.cco.caltech.edu/~aquaria/Faq/plant.html

Aquarium.Net DIY Projectshttp://www.aquarium.net/diy/DIYindex.sht

Indoor Plant Grow Light Guide

HID Grow Lights | Fluorescent Grow Lights | Incandescent Grow LightsLED Grow Lights | Electrical Cost | Sunlight's Effect on Plant Growth

Horticultural lighting systems allow you to extend the growing season by providingyour plants with an indoor equivalent to sunlight. This is a great advantage for thoseof you who appreciate having a year-round supply of fresh flowers, veggies andherbs. Artificial lighting is also a great way to jump-start spring by starting yourseedlings months ahead of the last frost. There are three main types of horticulturallighting systems.

Light Output Comparison Chart
http://www.lighting.philips.com/nam/http://www.ge.com/lighting/business/products/starcoab.htmhttp://www.ge.com/lighting/business/products/spspx.htmhttp://www.sylvania.com/ic/products/t8.htmhttp://www.cco.caltech.edu/~aquaria/Faq/plant.htmlhttp://www.aquarium.net/diy/DIYindex.shthttp://www.littlegreenhouse.com/guide3.shtml#hidhttp://www.littlegreenhouse.com/guide3.shtml#fluhttp://www.littlegreenhouse.com/guide3.shtml#inchttp://www.littlegreenhouse.com/guide3.shtml#ledhttp://www.littlegreenhouse.com/guide3.shtml#costhttp://www.littlegreenhouse.com/guide3.shtml#effecthttp://www.lighting.philips.com/nam/http://www.ge.com/lighting/business/products/starcoab.htmhttp://www.ge.com/lighting/business/products/spspx.htmhttp://www.sylvania.com/ic/products/t8.htmhttp://www.cco.caltech.edu/~aquaria/Faq/plant.htmlhttp://www.aquarium.net/diy/DIYindex.shthttp://www.littlegreenhouse.com/guide3.shtml#hidhttp://www.littlegreenhouse.com/guide3.shtml#fluhttp://www.littlegreenhouse.com/guide3.shtml#inchttp://www.littlegreenhouse.com/guide3.shtml#ledhttp://www.littlegreenhouse.com/guide3.shtml#costhttp://www.littlegreenhouse.com/guide3.shtml#effect


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Each scenario above represents approximately 50,000lumens.

HID (High Intensity Discharge) Plant Grow Lights

HID lighting is the most efficient way to convert electricity into light that is availableto the consumer. There are two types of HID grow lights used for horticultural

lighting:

Metal Halide - MHMetal halide bulbs produce an abundance of lightin the blue spectrum. This color of light promotesplant growth and is excellent for green leafygrowth and keeping plants compact. It is the besttype of light to be used as a primary light source(if no or little natural sunlight is available). Theaverage lifespan is about 10,000 cumulativehours. The bulb will light up beyond this time butdue to the gradual decline of light, it is not worthyour while to wait for the bulb to finally burn out.

If you compare their lumen (brightness) per unitof energy consumed, metal halides produce up to125 lumens per watt compared to 39 lumens perwatt with standard fluorescent lights and 18lumens per watt for standard incandescent bulbs.View self-contained HID grow lights, View remoteballast HID grow lights

High Pressure Sodium - HPSHigh pressure sodium bulbs emit an orange-red

glow. This band of light triggers hormones in plantsto increase flowering/budding in plants. They arethe best grow lights available for secondary orsupplemental lighting (used in conjunction withnatural sunlight). This is ideal for greenhousegrowing applications.

Not only is this a great flowering light, it has twofeatures that make it a more economical choice.
http://www.littlegreenhouse.com/accessory/lights2.shtml#minihttp://www.littlegreenhouse.com/accessory/lights3.shtmlhttp://www.littlegreenhouse.com/accessory/lights3.shtmlhttp://www.littlegreenhouse.com/accessory/lights2.shtml#minihttp://www.littlegreenhouse.com/accessory/lights3.shtmlhttp://www.littlegreenhouse.com/accessory/lights3.shtml


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Their average lifespan is twice that of metal halides, but after 18,000 hours of use,they will start to draw more electricity than their rated watts while graduallyproducing less light. HPS bulbs are very efficient. They produce up to 140 lumens perwatt. Their disadvantage is they are deficient in the blue spectrum. If a gardenerwere to start a young plant under a HPS bulb, she/he would see impressive verticalgrowth. In fact, probably too impressive. Most plants would grow up thin and lanky

and in no time you will have to prune your plant back before it grows into the lightfixture. The exception to this is using HPS grow lights in a greenhouse or inconjunction another light source that emits light in the blue spectrum. Light sourcesthat have a high output in the blue spectrum like sunlight and MH grow lights offsetany stretching caused by HPS bulbs. View self-contained HID grow lights, Viewremote ballast HID grow lights

HID Light Output Primary Growing AreaSupplemental Growing

Area

100 watts 2' x 2' 3' x 3'

250 watts 3' x 3' 5' x 5'

400 watts 5' x 5' 8' x 8'

600 watts 6' x 6' 10' x 10'

1000 watts 8' x 8' 12' x 12'

HID Lighting Helpful Tips

. Hanging height: Due to the heat that is emitted from these types of fixtures,you should hang them according to size. Smaller wattage systems(100 and 250) should be hung about 2 to 3 feet from the top of theplants. Medium wattage systems (400 and 600) should be hungaround 4 feet from the top of the plants. High wattage systems (1000and up) should be placed at least 4 to 6 feet from the plant tops.

. How long should lights run?This depends on the type of plant.

Most plants and vegetables need about 10 to 12 hours of light to promote growth.Plants that produce fruits or flowers will show improvement with up to 16 hours a dayof supplemental light.

Fluorescent Plant Grow Lights

Until recently, flu

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