Agri Kultuur August / Augustus 2018 | Page 12

Microbial diversity in Aquaponics Systems Henk Stander Aquaculture Division, Department of Animal Sciences, Faculty of AgriSciences, University of Stellenbosch T he word “aquaponics” comes from two separate words, which are combined. The first word is “aqua”, which of course, means water, but in this case, the “aqua” is from another compound word “aquaculture” (the production or raising of fish as a livelihood). The second word is “ponics”, which is Latin for work, and comes from its use in “hydroponics” (working, at growing plants in water, hydro). Aquaponics refers to any system that combines conventional aquaculture with hydroponics in a symbiotic environment. In normal aquaculture, excretions from the animals being raised can accumulate in the water, increasing toxicity. In an aquaponics system, water from an aquaculture system is fed to a hydroponic system where the by-products are broken down by nitrifying bacteria initially into nitrites and subsequently into nitrates that are utilized by the plants as nutrients. The water is then recirculated back AgriKultuur |AgriCulture to the aquaculture system. Aquaponics systems are recirculating aquaculture systems that incorporate the production of plants without soil. Intensive recirculating systems are designed to raise large quantities of fish in relatively small volumes of water by treating the water to remove toxic waste products and then reusing it. In the process of reusing the water many times, non-toxic nutrients and organic matter accumulate. These metabolic by-products need not to be wasted if they are channelled into secondary crops that have economic value or in some way benefit the primary fish production system. Systems that grow additional crops by utilizing by-products from the production of the primary species are referred to as integrated systems. If the secondary crops are aquatic or terrestrial plants grown in conjunction with fish, this integrated system is referred to as an aquaponics system. 12