LAYOUT OF A FISH FARMINTRODUCTIONThroughout the centuries fish has been an important component of the population’s diet in many parts of the world. Natural fishes which are caught all over the world, are not enough to meet requirement of people. So it is necessary to culture more fish. For the culturing of fish the first important thing is to construct a fish farm.

ADVANTAGES OF FISH FARMING Fish provides high quality animal protein for human consumption. A farmer can often integrate fish farming into the existing farm to

create additional income and improve its water management. Fish growth in ponds can be controlled: the farmers themselves select

the fish species they wish to raise. The fish produced in a pond are the owner's property; they are secure

and can be harvested at will. Fish in wild waters are free for all and make an individual share in the common catch uncertain.

Fish in a pond are usually close at hand. Effective land use: effective use of marginal land e.g. land that is too

poor, or too costly to drain for agriculture can be profitably devoted to fish farming provided that it is suitably prepared

METHODS OF FISH FARMINGFish farming may range from ‘backyard’ subsistence ponds to large-scale industrial enterprises. Generally there are three methods of fish farming system which are adopted by the fish farmers, such as:

Extensive. Semi-intensive. Intensive

Extensive:

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Fish farming, economic and labor inputs are usually low. Natural food production plays a very important role, and the system’s productivity is relatively low. Fertilizer may be used to increase fertility and thus fish production.

Semi-intensive:

Fish farming requires a moderate level of inputs and fish production is increased by the use of fertilizer and/or supplementary feeding. This means higher labor and feed costs, but higher fish yields usually more than compensate for this.

Intensive:

Fish farming involves a high level of inputs and stocking the ponds with as many fish as possible. The fish are fed supplementary feed, while natural food production plays a minor role. In this system, difficult management problems can arise caused by high fish stocking densities (increased susceptibility to diseases and dissolved oxygen shortage). The high production costs force one to fetch a high market price in order to make the fish farm economically feasible.

Following matters should be consideredLocation A land with a gentle slope should be

selected.

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Construction Ponds may be dug into the ground; they may be partly above or below original ground level. Slopes and bottom should be well packed during construction to prevent erosion and seepage. Soil should contain a minimum of 25% clay. Rocks, grass, branches and other undesirable objects should be eliminated from the dikes.

Pond depth Depth should be 0.5-1.0 m at shallow end, sloping to 1.5-2.0 m at the drain end.

Configuration Best shape for ponds is rectangular or square.

Side slopes Construct ponds with 2:1 or 3:1 slopes on all sides.

Drain Gate valves, baffle boards or tilt-over standpipes should be provided. Draining should take no more than 3 days.

Inflow lines Inflow lines should be of sufficient capacity to fill each pond within 3 days. If surface water is used, the incoming water should be filtered to remove undesirable plants or animals.

Total water volume Sufficient water should be available to fill all ponds on the farm within a few weeks and to keep them full throughout the growing season.

Dikes Dikes should be sufficiently wide enough to allow mowing. Dike roads should be made of gravel. Grass should be planted on all dikes.

Orientation Locate ponds carefully to take advantage of water mixing by the wind. In areas where wind causes extensive wave erosion of dikes,

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place long sides of pond at right angles to the prevailing wind. Use hedge or tree wind breaks where necessary.

DIFFERENT POND TYPESDepending on the site, there are two different types of fish ponds to choose from: diversion or barrage ponds.

DIVERSION PONDS : Diversion ponds are constructed by bringing water from another source to the pond.

Figure: Diversion pond: A: stream, B: water intake, C: diversion canal, D: inlet, E: outlet.Diversion ponds are of three types

EMBANKMENT PONDS: The dikes of an embankment pond are built above ground level. A disadvantage of this type of pond is that you may need a pump to fill the pond.

EXCAVATED PONDS: An excavated pond is dug out of the soil. The disadvantage of this type is that you need a pump to drain the pond.

CONTOUR PONDS:

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Soil from digging out the pond is used to build the low dikes of the pond. The ideal site has a slight slope (1-2%) so the water supply channel can be constructed slightly above and the discharge channel slightly below the pond water level. Since natural gravity is used to fill and drain the ponds, no pump is needed.

Figure: Different

types of diversion ponds A: embankment pond B: excavated pond; C: contour pond.1. Pump, 2. Drainage canal, 3. Inlet pipe, 4.Diversion canal, 5. Overflow pipe

BARRAGE PONDS:Barrage ponds are constructed by building a dike across a natural stream. The ponds are therefore like small conservation dams with the advantage that they are easy to construct. However, it is very difficult to control this system: it is difficult to keep wild fish out and a lot of feed added to the pond will be lost because of the current. A properly built barrage pond overflows only under unusual circumstances.

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Figure: Barrage pond. A: stream, B: inlet, C: dam, D: outlet pipe, E: spillway and overflow, F: monk (One of the most common pond draining structures. It consists of a vertical tower with boards to regulate the water level; a pipeline to discharge the water; and a screen to prevent farmed fish from escaping the pond)

CONSIDERATION DURING PLANNIG A FISH FARMLAND AREA:

Establish that the land is relatively level. Steeply sloped land is not generally suitable for building ponds. A slope of about 1% is considered ideal.Determine that the area is large enough for your present plans and for any future expansion.The area should not be prone to flooding. Study weather records for the area, ask local residents about flooding in recent years, and look for actual evidence that flooding has occurred.The area should not be subject to pollution in runoff from adjacent land. Find out who owns adjacent and uphill land, how they use the land, and what chemicals (including fertilizers and pesticides) they use.If possible, the land must be slightly lower than the water source, so that the ponds can be filled by gravity rather than by pumping. Supplying water by gravity greatly reduces energy inputs and operating costs.In most cases the larger the surface area (with gentle slope), the better. This is only true if the land and water are not expensive.Consider development plans for neighboring areas and assess any causes for concern.

WATER SUPPLYThe most common sources of water used for aquaculture are surface waters (streams, springs, lakes) and groundwater (wells, aquifers). Of these, wells and springs are generally preferred for their consistently high water quality.

The quantity and quality of water should be adequate to support production through seasonal fluctuations.Determine that the quality of the intended water source is good enough for fish to thrive in. A good water source will be relatively free of silt, aquatic insects,

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Other potential predators, and toxic substances, and it will have a high concentration of dissolved oxygen.If fish are already living and reproducing in the water (for example a river or lake), this is usually an indication that the quality is good.Find out if the quality remains constant throughout the year or if there are seasonal changes that result in poor quality at certain times.Make the final site selection based on both the quality and quantity of water available.The quantity of water required depends on the species to be cultured and on the anticipated management practices, for example whether ponds will be operated as static ponds (no water flowing through) or as flow-through systems.Coldwater species like trout require a lot of water because they prefer a continuous supply of clean water with high dissolved oxygen concentrations (above 9 mg/L).Warm water species like tilapia can tolerate water with lower dissolved oxygen levels, so tilapia culture is often done in static water, that is, without water flowing through the ponds. However, the best situation is to have a lot of “free” water, meaning water available by gravity flow, even if it is not always being used. For earthen ponds, the water source should be able to provide at least 1 m3 of water (1000 liters) per minute for each hectare of ponds that will be built. This quantity will be sufficient for quickly filling the ponds as well as for maintaining water levels throughout the culture period.If the selected site has relatively poor soils (i.e., soils containing too much sand) the source should be able to provide two to three times more water (2-3 m3 per minute per hectare). This quantity of water will be sufficient for maintaining water levels to compensate for losses that are likely to occur through seepage.

SOILo Land should be comprised of good quality soil, with little or no

gravel or rocks either on the surface or mixed in. Areas with rocky, gravelly, or sandy soil are not suitable for pond construction.

o The soil should be deep, extending down at least 1 meter below the surface. There should not be layers of rock lying close to the surface.

o Soils in the area where ponds will be built should have clay layers somewhere below the surface to prevent downward seepage.

o Soil that will be used to build the dykes must contain at least 20% clay so the finished pond will hold water throughout the growing period.

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o Some soil with a higher clay content—preferably between 30 and 40%—should be available nearby. It will be used to pack the core trenches in the dykes.

PROXIMITY TO A MARKETDoes market demand justify production?Will the existing physical infrastructure meet the farmer’s needs for marketing the fish?Will there be sufficient demand nearby or will transporting to a distant market often be a necessity?

It is easier to sell at your doorstep or to have a permanent buyer who takes everything we can produce and either picks the fish up or is close enough that you can deliver the fish to them.

INFRASTRUCTUREAre the roads good enough to bring supplies to the farm and take the product to the market?Are telephone service and electrical power available at the site?If an intensive production system is necessary due to constraints of space or water, access to power is a must. Electrical power is about two times cheaper than diesel power in Kenya (2006 prices).Telephone service may be needed for ordering supplies, arranging marketing, or requesting technical assistance.

Availability of needed inputsAre fertilizers and lime available at reasonable cost?Are fingerlings available at a reasonable cost?Are fish feeds available for purchase, or are suitable ingredientsAvailable so the farmer can produce his own?

. ACCESS TO TECHNICAL ADVICEBe sure good technical advice is readily available. Local extension agents or trained consultants are good possibilities. Remember: technical advice can be expensive and is sometimes wrong. Double-check advice received with a qualified individual (meaning they have produced a few tons of fish before) who is sincerely interested in your success. Good consultants admit when they don’t know the needed information.Consider both criticism and compliments very carefully: The best advice may come in the form of criticism, and compliments can be misleading.

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Horticulture and animal husbandry consultants may know about business planning for agriculture but probably do not know enough about fish farming to give proper technical advice.

COMPETITIONKnow who your competitors are and how much they sell their fish for. Consider whether you will be able to match their price and quality or even outsell them by producing a better product or selling at a lower price. If fish demand is high, cooperating with nearby fish producers to market the fish might be a possibility. The presence of several fish farmers in an area may make it possible for inputs to be obtained less expensively by forming a purchasing block (cooperative or group).

LEGAL ISSUESConsider whether or not there are any legal issues that will affect your ability to culture fish at this site. For this the following matter should be considered-

Land Use Act, Water Act, Environmental Management and Coordination Act, others.

POND DESIGN AND LAYOUTLAYOUT OF PONDS

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It is very important to consider the layout of the ponds in relation to the topography of land, the source of water, and drainage. Also important is to allow for expansion of the fish farm at a later stage. The ponds, drainage canals and other facilities should be laid out in such a way that additional

ponds can be constructed at a later stage. A well-built pond is easier to operate, so careful attention to all the features of a pond will be well rewarded later. Below are features found in a well-built pond?

POND SIZE AND SHAPE

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Figure: Layout of a fish farm

Ponds of 500–2000m2 are easy to manage by household farmers. Although the number of ponds is an individual decision, a few large ponds will be cheaper to construct than many small ponds of the same total surface area. Most farmers build rectangular ponds, though irregularly shaped and even round ponds have been built. With rectangular ponds, the long axis of the pond can be placed to take advantage of winds blowing across the pond that aerate the water. In places where high winds are a problem, the long axis can be built parallel to the prevailing wind, thus minimizing erosion from waves. In addition, rectangular ponds are more suitable for harvesting fish with a net. The length of the pond does not matter much but the preferred width is 15–20 meters, to suit the standard size of seine nets used for harvesting.

POND BOTTOMIn order for the water to drain out,

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the pond bottom slopes gently towards the outlet end of the pond. A minimum bottom slope of 0.1–0.2% is recommended. The pond bottom should be smooth and free from bumps and hollows, to make it easier

to haul the seine nets and to catch as many fish as possible. A catch pit or harvesting sump may be excavated around the water outlet. Fish will swim into this pit as pond water drains out. The catch pit should be big enough to be able to contain almost all the fish in the pond at the time of harvesting. It also needs to have a supply of fresh water and/or aeration for the period that fish are concentrated in it.

POND DEPTHThe pond depth is usually in the range 1–2m, and often is a compromise determined by topography, water source and soil. Ideally pond water depth should be 0.8m at the shallow end, and increase gradually to 1.2m at the deep end, with 30–50cm of freeboard (level of dyke above water, see Fig. 6). Ponds entirely dependent on seasonal rains must be deeper in order to hold water longer into the dry season, for example water depth of 1.0–1.5m. Maintaining the right depth of water helps to regulate temperature, inhibit growth of underwater plants and maintain dissolved oxygen (DO) levels at the pond bottom, which helps the organic decomposition that provides nutrients for the growth of phytoplankton and zooplankton, microscopic organisms that will in turn provide food for the fish.

Fig. : Cross-section of pond along length of the pond

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DYKEDykes are also called dikes, banks, walls, embankments and bunds. The dyke is the part of the pond above the natural ground and is for retaining the water. It is important that the dyke walls are sloped to prevent erosion and avoid enlarging of the pond. The slope on the inside of the dyke should be somewhere from 2:1 to 3:1. The slope on the outside of the dyke can be steeper at about 1.5:1 to 2:1, but when there is a series of ponds next to one another the slopes for both sides of the dyke will be the same. The amount of slope depends on the type of soil used to make the dyke.

Dykes made of clay soils can have steeper slopes than dykes made of soft soils such as sandy loam. In hand-dug ponds the width at the top should be about the same as the height of the dyke (see Fig. 7). Where the ponds are excavated by machines, the top width is dependent on the width of the machine base (track) as well as on the type of soil and size of the pond. The soil used for the dyke should not contain large amounts of rocks, sand, wood, grass or plants, as these will cause the dyke to leak water. Do not plant crops with big tap roots on dykes, as digging them up again will weaken the dyke.

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Fig.: Dyke cross-section

WATER INLETAn inlet is to let water into the pond. The location of the inlet will depend on the shape of the land in relation to the water source. There are various types of inlets that can be used, for example PVC pipe, polyethylene pipe, galvanized pipe, open earth canal, concrete channel, pump etc. PCV pipes are expensive but are used commonly as they are easy to install, durable, and make it easy to control the water supply. A PVC pipe of 25–50mm in diameter is sufficient in most cases. An earth channel going direct into the pond is cheapest and easiest to make, but it is cumbersome to screen and to control the water supply. Water flowing through the channel also cuts into the soil where it enters the pond, causing erosion the flow of water into each pond must be controlled by valves (if piped) or shut-gates. Water inlets should have a screen to keep out wild fish, twigs, leaves and other trash. Each pond should have its own individual water supply from a central water distribution pipe or channel that brings water from the water source. No pond should receive the water outflow from any other pond. Transfer of water from one pond to another is not recommended since it means poorer water quality conditions in the next pond, and brings the risk of disease transfer. There should also not be any contact between incoming water and water drained out from ponds. Ideally, water should be distributed to ponds by gravity, if the land topography allows it. This means the water source and inlet pipes or channels need to be at a level higher than the pond water level.

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WATER OUTLETAn outlet is to let water flow out of the pond. The outlet should be at the deepest end of the pond so that all the water can be drained out of the pond by gravity. There are several types of outlets that can be used: for example PVC pipe, siphon, or pump. If the outlet has an up stand pipe mounted on an elbow fitting (Fig. 8) then it can control the water level in the pond. To drain the pond, the up stand pipe is turned on its elbow and laid down flat. At other times it is tied to a pole driven into the ground to prevent it falling over and accidentally draining the pond. A PVC outlet and up stand pipe is more expensive, but this is the most common type of outlet used in the Pacific. The diameter of the outlet pipe depends on the size of the pond. Usually 100–150mm is adequate for small (500–1000m2) ponds. For larger size ponds, pipes with a larger diameter can be used, or several 100mm pipes. A larger diameter pipe allows for quicker drain-down of ponds during harvesting. Outlets pipes should have a screen on the end inside the pond to prevent the fish escaping.

WATER OVERFLOW PIPEAn overflow is an extra pipe to let excess water flow away during heavy rainfall. It should be placed towards the outlet side, about 20–30cm below the top of the dyke, about 20cm above normal water level. The overflow pipe should also have screen to prevent the fish escaping.

SCREENSBox screens on the water inlet to prevent pest fish entering the pond are common and effective. A cloth filter on the inlet may be necessary to remove fish eggs if water is being obtained from a river or canals containing fish (see

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Fig. 10). Initially, 1-mm galvanized or plastic mesh screen (similar to mosquito screen) is used on both the inlet and outlet. The outlet screen can be changed to a larger mesh every month as the fish grow. Screens will need to be checked regularly for clogging.

CONSTRUUCTION OF POND Ponds dug by hand are generally small (100–300m2). The tools required for digging include: spade, hoe, mud-scoop spade, fork, wheelbarrow and wooden mullet (ram). The steps in construction are as follows.

MARKING THE POND AREA1. First, prepare a sketch plan of the pond area.2. Clear the entire area of the fishpond of all grasses, trees, stumps. These could be burned or removed from the site. It is important to dig a channel or drain to allow water to drain away from the construction site.3. To outline the dimensions of the pond, first mark the outside edge of the dyke using wooden or bamboo stakes. For example, for a pond that will have approximately 24m x 14m of water surface area, mark out a boundary measuring 30m x 20m. This will allow for a dyke around the pond that will be about 3m thick at ground level. For bigger ponds, use the same dyke-width dimension and just make the central area bigger on the plan. The corners of this rectangle can be marked with pegs, and a string can be run between the pegs.4. In order to get rid of roots, remove about 10–20cm of topsoil from throughout the 30m x 20m marked area. It is important that there should not be any roots or dead grass in the dyke for water to leak through later. Note that the topsoil removed needs to be set aside, to be put back later on the top and outer sides of the pond dyke. 5. Next, mark out a smaller rectangle of 24 x 14m inside the bigger (30 x 20m) rectangle. This will show where the inside of the dykes will be at ground level. This 24 x 14m rectangle is the area of ground that is going to be dug. The earth that is dug out will be used to make the tops of the dykes. The bottom of the dyke in the shallow end of the pond will begin from about another 1.5m inside this smaller rectangle. The bottom of the bank in the deepest part of the pond will be about 2m from the lower end of this smaller rectangle.6. Then mark a third rectangle in the center of the pond, measuring about 21m x 11m. This is called the central area, and represents the flat bottom of the pond.

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Fig. Ground plan for a hand-dug pond (top) and cross-section of pond along A-B (bottom) the digging process

The central 21m x 11m area is dug out first, and the soil is used to build the dyke of the pond. The workers should be organized in a row with shovels and digging forks. The digging begins at the shallow end of the pond, at the string marking the central area. The pond is dug to about 20cm deep at the shallow end, increasing gradually in depth towards the other end. At the deepest part, at the string marking the central area the depth should be about 30cm.As the soil is dug out, it should be placed in the space marked out for the dyke, between the 24m x 14m rectangle and the 30m x 20m rectangle. It is recommended that the soil be placed nearest to the digging area so that the dyke will become higher and wider towards the deeper end. Whenever the loose soil placed on the dyke reaches about 30cm (knee height), it should be packed down tightly. This can be done by compacting the soil with a heavy length of tree trunk. It is very important to ensure that the slope of the pond bottom be made as regular as possible. Once the first 20–30cm layer of soil from the central part has been dug out, the whole process can be repeated to take out another layer. As before, begin the process by digging out 20cm deep at the shallow end and 30cm deep at the other end. As before, the soil removed is placed on the dyke area and packed down tightly. Then, for a third and last time, another layer of soil is dug out of the central area and packed down tightly on the dyke.

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SHAPING THE DYKEWhen the digging is finished in the central area, there will be a hole 21m x 11m with straight sides. The dyke can be then shaped by digging the soil away from the edges of the central area to form a slope up to the 24m x 14m string. This soil can be placed on top of the dyke and packed down tightly with the slope continued smoothly up to the top. The inside of the dyke should slope more gently than the outside (except where two ponds are built side by side). Fig. 7 shows what the dyke should look like when finished. The top of the dyke should be about 1.5m wide, and flat all the way around the pond. The topsoil removed at the beginning should now be placed on the top and outer sides of the dyke. The bottom of the pond should be about 1.3m below the top of the dyke at the shallow end, and about 1.7m below the top of the dyke at the deep end. The bottom of the pond should be fairly smooth and regular. All loose soil and other trash from the bottom of the pond should be removed.

PONDS SIDE BY SIDEWhen marking out ponds to be built side by side, leave an extra 1.5–2m between the two big rectangles (30m x 20m markers) to allow for the slopes of the dykes inside the adjoining ponds.

INSTALLING THE WATER INLETA water inlet is required to fill the pond with water. This inlet should be placed at the point nearest to the water source. Most often this will be at or near the shallow end of the pond. An inlet pipe should be 25–50mm in diameter, and long enough to reach across the top of the dyke from one side to the other. Once the position of the inlet is decided, dig a ditch across the dyke. This should be dug to a level to allow water to flow from the channel or 18 | P a g e

Figure: ponds side by side

pipe that brings the water from the water source and into the pond a little above the water level on the inside of the dyke. The inlet pipe can be placed in the ditch in the dyke, and the dyke rebuilt over it. Alternatively, if an open channel is used to allow water into the pond, erosion of dyke soil can be prevented by using roofing iron or hard plastic to line the bottom of the channel.

INSTALLING THE WATER OUTLET The water outlet is made at the bottom of the dyke at the deepest end of the pond (Fig. 6). The outlet is usually made from PVC pipe and should be at least 100mm in diameter. Since the dyke at the deep end will be wider than at the shallow end, and the outlet pipe is installed at the bottom of the dyke, the widest part, several meters of outlet pipe will be needed. It may be possible to join pieces of pipe together to make the required length.A gap or ditch is dug through the dyke where the outlet is to be located. It should reach from the deepest part on the inside of the pond through the dyke to a lower level outside of the pond, to allow water to drain from the pond. If the outlet is below ground level on the outside of the pond, it will be necessary to dig a drain to take the water away from the outlet. The outlet pipe is placed in the gap in the dyke and the dyke is rebuilt over it.

INSTALLING AN UP STAND PIPE The water level in the pond can be regulated by an up stand pipe. This is mounted on the outlet pipe in an upright position, usually on the end outside the pond, using an elbow fitting. Alternatively, the up stand pipe could be installed inside the pond at the entrance to the outlet pipe, to avoid accidental drainage of the pond, although the outside position is preferable, as it allows the excess water to be drained off from the bottom of the pond. The top of the upright pipe should be at about 3–5cm above the water level of the pond. If water rises above this level, it will overflow into the drain. The up stand pipe should be tied securely to a pole driven into the ground, so that it does not slip down accidentally and let the water out of the pond. When the pond needs to be emptied, the up stand pipe can be untied and gently pushed down, allowing water to flow out of the pond gradually.

USING A SIPHONDuring harvesting and other times, a siphon can also be used to increase the flow of water out of the pond. This could be a 25–50mm flexible hose, long

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enough to reach over the dyke from pond to drainage ditch. It must be long enough to extend from the deepest part of the pond, over the top of the dyke and down to the level of the drain on the other side of the dyke (10–20m long). To activate the flow of water, the hose must first be completely filled with water, with no air spaces inside it. One end must be covered with a tightly sealing plug or end-cap and the other end left open. This open end stays underwater, while the closed end is pulled over the dyke and down into the drainage ditch. Unplugging this end will then cause the water to flow rapidly out of the pond.

SCREENING INLET AND OUTLETS Care must be taken to place screens on the inlet, the outlet pipe and overflow pipe to prevent fish from escaping as well as stop other fish from entering the pond.

Figure: Mesh screen on inlet pipe

MAINTENANCE AND MONITORINGTo achieve a high production of fish in the pond, regular maintenance and monitoring is vital. Daily management includes:

Checking the water quality (oxygen, pH, color, transparency, temperature, etc.)

Checking the pond for possible water leaks Cleaning the screen of the water inlet and outlet Observing the fish while they feed: Do they eat normally? Are they

active? If not, and if they are gasping for air at the surface, the oxygen level in the water is too low. Stop feeding and fertilizing and let water flow through the pond until the fish behave normally again. Otherwise, look for symptoms that could indicate a disease.

Watching out for predators, or signs of predators such as footprints, and taking precautions if necessary.

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Removing aquatic weeds growing in the pond.

Water quality is a vital factor for good health and growth in fish. Some of the most important water characteristics are described below.

CONLUSIONFor the successful aquaculture farming operation, the first criteria is to design a proper & planned layout. Fish farmer should have to maintain all the necessary steps for the best production, which is economically positive. So it is very important to raise the awareness of fish farmers to design an appropriate layout before making a fish farm.

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