Aquaponics Systems
Fluid Mechanics, Plant Care and Fish Care in Aquaponics
​Fluid flow, mechanical pumps and system capacity
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Pumps
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A water pump should circulate the entire volume of water in your system at least every 2 hours
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Requires 1 psi to raise the water level 2.2 feet
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Need to keep in mind the head height (distance between the fish tank and the grow bed)
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Need a pump with at least 100 GPH (however should select a pump with a higher GPH than required because the number is a maximum and can be dialed down)
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Grow Bed
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Industry standard is at least 30 cm deep
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Fish tank volume should be approximately equal to grow bed volume or you can extend it to be a 2:1 ratio
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Other
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Stocking Density: 1 pound of fish for every 5-10 gallons of water
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Ammonia and nitrate levels should be less than 0.75 ppm
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Plant Care
Generally, the best plants to grow in an aquaponics system are leafy greens, such as chard or watercress, because they have lower nutrient needs. This allows a system to grow more plant mass with less fish and therefore less upkeep.
Plants generally grown with good results: any leafy lettuce, bak choi, kale, swiss chard, arugula, basil, mint, watercress, and chives​
Plant Cycle:
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Aquaponics systems aim to reduce the amount of toxic fertilizer runoff and water waste through a quasi-closed loop biofiltration system
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Utilizes nitrogen-rich fish effluent to fertilize plants grown in soilless, floating beds
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Nitrifying bacteria pay a key role in aquaponics because they oxidize ammonia or nitrite, which is toxic to the fish in the system, into nitrate which plants uptake
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Role of Nitrates/Nitrites:
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The balance of of nitrite concentrations is important in aquaponics plant care because too high concentrations can lead to fish death, and too low concentrations will not properly fertilize the plants being grown
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It is also important to properly filter the effluent before it cycles through plant beds, for the wellbeing of the plants and fish
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Solid waste should be removed from effluent through a preliminary filter
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The extent of filtration depends on the relative concentrations of fish to plants
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Fish Care
Fish generally raised with good results: tilapia, bluegill/brim, sunfish, crappie, koi, fancy goldfish, pacu, angelfish, guppies, tetras
Tank Requirements:
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Fish tank can be glass, plexiglass, plastic tub/bucket/barrel, recommended to be anywhere between 3 and 20 gallons, although larger sizes can be used if the space is available
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Ideally fish tank is in the shade because sunlights fuels algae growth
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The larger the tank, the larger grow bed area you can support; as a general rule of thumb, 10 gallons of fish tank water can support 1-2 square feet of growing area
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Planting aquatic plants in a fish tank provide a more natural habitat for the fish and aid in water purification
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Many pesticides that are safe for plant use in soil are not safe for aquaponics systems because they can be toxic to the fish in the system
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Water temperature should be monitored throughout the system, taking into consideration plant and fish species needs - ideal temperature is around 75℉
Fish Cycle:
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Fish excrete ammonia through both their waste and gills, a substance that can be toxic to fish and plants in large enough quantities
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Nitrifying bacteria, which live and survive naturally in soils, water and air, convert this ammonia to nitrite and then to nitrate
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In aquaponics systems, these bacteria will thrive in both the fish tank gravel and in the grow bed medium
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Plants readily uptake nitrate from the water and consume it, keeping ammonia levels safe for fish and plants to live
Fish Care:
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The only daily input in aquaponics systems is fish food
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Most fish (including tropical fish) do well on dry flake fish food, being fed in small but frequent quantities
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The water level in the tank will decrease as water is absorbed by the plants throughout the system, requiring that the tank be refilled every few days
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Once a month, 10-15% of the water should be siphoned out and replaced with fresh water
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