Aquaponic results in the synergy of fish farming and above-ground plan cultivation. Its objective is to produce fish and plants through water circulating between the two systems. The main input to the system is feed for fish whose excrements will be recycled for plant nutrition. To feed fish more sustainably, worms from composts are preferable to industrial meal. The nutrients in the droppings are made available to plants by bacteria. The system consists of two tanks: one containing plants and the other containing fish.
Fish (or crustaceans) produce droppings in the water, which are sources of ammonia. The water containing this organic waste is then conveyed to the cultivation tank through a filter containing bacteria (Nitrosomonas). These transform ammonia into nitrite, which is then converted into nitrate by Nitrobacter and Nitrospira. Nitrate is then directly assimilated by the roots of plants. The water purified by plants from the cultivation tank is then recirculated into the fish pond.
The most suitable fish for pond farming conditions are freshwater fish, omnivorous or carnivorous, such as: common carp, rainbow trout, perch or tilapia. Due to their lower nutrient requirements, the most cultivated plants are often green vegetables (lettuce, spinach, leek, chard) and aromatics (basil, parsley, chives). They can be planted on gravel, clay balls or mineral wool moss depending on their root system.
Aquaponics is part of an agroecological approach, allowing a closed nutrient cycle. The objective is to recycle the waste from one activity in order to limit external inputs for another activity. This system also saves up to 95% of water compared to soil cultivation and is productive on small areas.
References to explore
Graber A., Junge R. 2009. Aquaponic Systems: Nutrient recycling from fish wastewater by vegetable production. Desalination, Volume 246, Issues 1–3, pp 147-156.
Somerville C., Cohen M., Pantanella E., Stankus A., Lovatelli A. 2014. Small-scale aquaponic food production : Integrated fish and plant farming. FAO Fisheries and Aquaculture Technical Paper No. 589. Rome, FAO. 288 p.