The principle of aquaponics is a combination of aquaculture (rearing of fish) and hydroponics (cultivation of crops) in a closed cycle, but in separate containers.
The crops grow in an inorganic substrate (for example gravel, mineral wool or clay pebbles) in containers that are regularly filled with nutrient-rich water from the fish tanks. In addition, there are other cultivation options, such as based on the nutrient film technique (plants usually grow in tubes and are lapped by a nutrient solution) or the deep-water culture (here the plants grow with the roots directly and permanently in oxygen-enriched water). In all cases, overflowing water is channeled back into the fish tanks.
The principle is based on the natural nitrogen cycle: Nitrifying bacteria at the fish tank bottom and in the substrate of the plant beets convert ammonium and ammonia from fish excretions via the intermediate product nitrite into nitrate, which serves as a nutrient for the crops.
A species of fish that is often cultured in aquaponic systmes is Thalapia, a genus of cichlid fishes. Other species may also be bred, but the ambient temperature is a decisive factor for this is – as it is also the case for the selection of the vegetables to be planted. Although the water temperature can be adjusted to the needs of plants and fish by means of heaters, heat pumps, air conditioners or the like, the additional electricity costs must be taken into account.
Advantages:
- Closed water and nutrient cycle: Fresh water supply is only necessary to compensate for losses due to evaporation or plant removal.
- Hydroponic plant breeding is more efficient in comparison to growing on soil regarding a higher yield, lower water consumption and less space requirement.
- No addition of artificial fertilizers to the plants, but use of processed fish excreta.
- Year round production is possible.
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