The global interest in aquaponics has increased since the industry became a mainstream farming technology in 2010. Several universities are involved in aquaponics research and a host of companies offer products for sale or provide training courses. As a result, the farming of fish and soilless plant crops in a closed, circular system has been refined and is now well understood; the commercial case for aquaponics is clear.
There are different forms of aquaponics, but in the simplest type, water circulates continuously between fish tanks, bacterial beds and plants at a rate of four cycles per hour. Fish convert their feed into growth and by-products, a primary component of which is ammonia, which is converted by the bacteria to nitrate. Plants utilise the nitrate, and allied macro- and micronutrients, for their metabolic and growth requirements, leaving the water clean to again return to the fish. Such a system will operate continuously for many years without the water needing to be exchanged as the filters and plants maintain excellent water quality for the fish. Water lost to evaporation, transpiration and harvested crops is replaced with new water.
NUTRIENTS FROM FISH WASTES Depending on the composition of the source water and crops being farmed, supplementation with iron, calcium and potassium may be required, but all other nutrients are provided via the fish wastes. This results in the situation where the waste from feeding the fish produces a secondary crop, usually more valuable than the fish themselves, with minimal additional supplements.
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