One of the most sustainable suppliers of animal protein is fish - along with insects, but this is still a cultural problem in our latitudes at the moment. In aquaponics, fish farming is combined with vegetable production in a resource-saving way.

More and more consumers prefer environmentally friendly and regionally produced food. New concepts of modern food production in non-rural areas and on small surfaces, such as urban farming, are attracting more and more interest. As early as the 1980s, US scientists experimented with an approach that combined two production systems.

The Tomatofish (Copyright)

Aquaponics systems combine fish farming (aquaculture) with plant cultivation in soilless substrates or without substrates at all (hydroponics) by means of a common water and nutrient cycle within a system - i.e. a water cycle. This is a new concept for operating regional agriculture in urban areas in an environmentally friendly, resource- and land-efficient way.

The energy costs are mainly for air conditioning the facility - cooling in summer, heating in winter. But a greenhouse can produce five to ten times the amount of biomaterial compared to open field cultivation. With the newer aquaponics systems, one kilogram of fish can be produced with 100 litres of water, as well as an additional five kilograms of tomatoes (IGB plant).

Today, sustainable and regional food production is possible in aquaponics farms. The Berlin-based Leibniz Institute of Freshwater Ecology and Inland Fisheries (IGB) has made a significant contribution to this: the "tomato fish" project of a research group led by Professor Werner Kloas quickly became known nationwide and led to the development and patenting of its own aquaponics system.

Tilapia, edible fish from the cichlid family, live there in a closed water circuit. If necessary, a one-way valve regulates the water withdrawal from the fish circuit in the direction of the tomato farm. After water treatment by a biofilter, the plants growing on substrate receive an ideal nutrient solution with the correct pH value. The water evaporating through the leaves is collected by an air-conditioner and fed back into the fish circuit.

As an example: In Spain's vegetable stronghold of Almeria, it takes about 180 litres of water to grow one kilogram of tomatoes. This has the consequence of far-reaching ecological effects and a sharply lower water table as well as increasingly salinated soils.

According to the World Wild Fund for Nature (WWF), agriculture and processing account for around 70 percent of global freshwater consumption. In contrast, aquaponics farms enable food production with a 50 to 90 percent reduction in water consumption: 50 percent savings in the old single-loop systems - simply because of the dual use of water. A dual-circuit system with water recovery even achieves a saving of 90 percent. In this production system, fresh water only has to compensate for losses due to evaporation and the removal of biomass from the system.

Modern aquaponics systems use a common heating system for both fish and plant cultivation. This reduces heat losses and uses energy more efficiently. Since energy sources such as the sun and biogas are used for heat and energy supply in the greenhouse and the tomatoes fix the carbon dioxide released by the fish, the IGB's aquaponics system can be operated almost CO₂-neutral and emission-free.

Fish are also very good feed converters and therefore one of the most sustainable suppliers of animal protein. One kilogram of fish can be produced in aquaponics farm systems with feed ratios similar to those of separate aquaculture cycle systems: One kilogram of feed yields about one kilogram of fish.