38
Overhead View of Aquaponic System
Hydroponic tanks
Fish production tanks
SumpClarifierNet tanks
Base additionDegassing
Fish Production Tanks
Four tanks per system Round tank with central drain
Water turnover rate once every 80 minutes
Tilapia Production Stocking and Harvesting
Stock 600, sex reversed, male Nile tilapia fingerlings/tank Average weight 50‐75 grams/fish
Drain and harvest tank 24 weeks later Average weight 700 – 750 grams/fish Survival greater than 95%
Staggered production Allows a tilapia harvest every 6 weeks A total of 2 harvests from each tank/year
Tilapia Diet Feed a floating diet with 32%
protein 3 times/day Feed ad libitum Expect FCR of 1.5 – 1.7
Achieve daily feeding rate of 60 – 100 grams of diet/m2 of hydroponic growing area/day Approximately 28 – 47 lbs of
feed/day/aquaponic system This is optimal amount for plant
production, balances the system, and minimizes water quality problems
Aeration 22 airstones/tank One, 1.5 horsepower regenerative
blower
Tilapia Production
Cylindro‐conical Clarifier Function
– Primary method for solids removal and discharge
– Baffled walls slow water velocity
Two units per system– Each unit receives
effluent from two fish tanks
Size– 1,000 gallons/unit
Water turnover rate – Once every 20 minutes
= 50 gallons/minute Sludge removed 2-3 times
daily
Cross Sectional View of Clarifier Removing Solids
Effluent Entering Clarifier from Fish Tank Effluent moving to Net Tanks to filter particulate matter
Baffled Wall
45o – 60o slope Area of concentrated settled solids for discharge
Effluent discharged from clarifier
Net Tanks Function
Capture suspended solids escaping clarifier
Allows solid matter to leach dissolved nutrients
Four units per commercial system
Need to be cleaned 1‐2 times weekly Cleaning affects nitrate concentrations and thus plant production
Cross Sectional View of Net Tank Filtering Suspended Solids
Mg+2
Ca+2
NO3-
NO3-
NO3-
NO3-
S+Mn+
NO3-
Degassing Tank
Heavy aeration blows off nitrogen gas and hydrogen sulfide produced in anaerobic environment of net tanks
Distributes water to hydroponic raceways Nets seen prevent tilapia fry from entering hydroponic raceways
Hydroponic Raceways Total of six raceways; 3 pairs
Each raceway is 100 ft x 4 ft x 1.3 ft Lined with LDPE food grade liner
Total of 72 polystyrene rafts per system; 12 rafts per raceway Each raft is 8 ft x 4 ft x 1.5 in
One, 1.0 Hp regenerative blower supplies oxygen for plants in all six raceways 25 airstones per raceway with 4‐foot spacing
Water turnover rate once every 180 minutes for each pair of raceways
Hydroponic raceways
Sump Lowest point in system
Water flows by gravity from fish tanks until it reaches the sump
The sump collects water from the hydroponic raceways before the water is pumped back to fish culture tanks
Site for water make up due to evaporation, transpiration and waste removal Float valve allows
make‐up water to enter
Base Addition Tank and Pump Base Addition Tank
Function Site for chemical base
addition to maintain optimum pH
Slowly adds base to sump via vigorous aeration
Site for nutrient supplementation
Pump Returns water from sump to fish culture tanks Pumps 100 gallons/minute
pH and base addition Must compromise pH for fish, plants and biofiltration
Fish prefer 7.5 – 8.5 Plants prefer 6.0 – 6.5 Nitrifying bacteria prefer 7.0 – 8.0
Maintain aquaponic system pH at 7.0 Calcium hydroxide [Ca(OH)2] and potassium hydroxide (KOH) added to increase pH when it falls below 7.0 Calcium hydroxide and potassium hydroxide added on alternate basis until pH returns to 7.0
Base used to supplement nutrients and neutralize pH
Calcium HydroxidePowder
Potassium HydroxidePrills/Flakes
Regenerative Blowers
Fish tank
Fish tank
Fish TankFish Tank
Clarifier
Clarifier
Sump
Net Tanks
Net Tanks
EffluentStorage
Plant Requirements There are 16 essential macronutrients and micronutrients for plant growth Macronutrients
N, P, K, Ca, S, Mg
Micronutrients B, Cl, Cu, Fe, Mo, Mn, Z
There are recommended ranges for aquaponic and hydroponic vegetable production Typically aquaponic nutrient levels are lower than recommended hydroponic nutrient levels Possible because fish are always creating effluent that passes through hydroponic raceways
Nutrient Supplementation Tilapia feed provides adequate levels of macronutrients
and micronutrients, but supplementation of calcium, potassium and iron required Calcium supplemented with addition of calcium hydroxide Potassium supplemented with addition of potassium hydroxide Iron supplemented with the addition of chelated iron to
maintain concentration of 2 mg/L
Plant Production Methods Batch Culture
One planting and one harvest of aquaponic system during plant production period Can quickly deplete nutrients as plants mature
Staggered Production Multiple plantings and harvests on a rotational basis
Prevents quick nutrient depletion Allows uniform nutrient uptake
Staggered Plant Production
Fish Tanks
Hydroponic Raceways
Harvesting a Staggered Crop
Push to end of raceway
Lettuce Production Seedlings require four weeks in the greenhouse before transplant into aquaponic system
Harvest after four weeks in the aquaponic system Leaf lettuce
Sierra 156 g/plant 60 seedlings/raft
Crisphead Montello 149 g/plant 60 seedlings/raft
Romaine Parris Island 204 g/plant 48 seedlings/raft
Bibb Boston bibb 88 g/plant 88 seedlings/raft
Basil Production Seedlings require three weeks in the greenhouse before transplant into aquaponic system
Harvest is dependent on management strategy Staggered production
Cut and come again Cut at 4 week intervals 3 months production
Cut 3 times then remove
48 plants/raft
Potential CropsMint Chives
Potential CropsCucumbers
Potential CropsCollard Greens Pak Choi
Potential CropsWater Spinach
Potential CropsCut Flowers & Melons
Principles to Remember Staggered fish and plant production maintains a balanced nutrient concentration in the system
Optimum fish feeding rate, 60 ‐ 100 g/m2 plantarea/day prevents nutrient accumulation ordeficiency
Frequency of net tank cleaning controls nitrate levels through denitrification
Base addition maintains optimal pH and supplements nutrients
Farmer’s shadow is best way to prevent and diagnose problems
Additional Information• Southern Regional Aquaculture Center (SRAC)
• SRAC Fact Sheets• Aquaponics
• https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/105/
• Tilapia Production• Life History and Biology
• https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/53/
• Tank Culture• https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/52/
• Recirculating Systems and Management• https://srac.tamu.edu/index.cfm/event/getFactSheet/whichfactsheet/103/
Additional Information
Questions
