Effect Of Aquafeed On Plant Productivity In An Aquaponic Production System.

Aquaponics is the combination of aquaculture and hydroponics in a recirculating system. Nitrifying bacteria in an aquaponic system convert the ammonium in fish waste to nitrate that fertilizes plants in a hydroponic grow bed. The plants filter the water so that it can be returned to the fish tank. Thus, aquaponics produces a plant crop in addition to the fish crop. Its potential for sustainable food security lies in the efficient use of water and space, the ability to produce crops independent of soil conditions, and the recycling of aquaculture effluent as a valuable input. Because aquafeed is the primary nutrient source in an aquaponic system, the choice of feed is crucial for the achievement of a sustainably-run system. This study compares the effect of two aquafeeds on water quality of effluent from cultivation of blue tilapia (Oreochromis aureus) and on productivity of an edible amaranth crop (Amaranthus tricolor) through statistical ANCOVA of periodically collected water samples and starting and ending plant biomass measurements. Water quality parameters include pH, EC, temperature, turbidity, dissolved oxygen, total ammonia-N, nitrite-N, nitrate-N and total phosphate. The control treatment consists of a typical soymeal aquafeed, while the experimental treatment consists of an alternative feed (algae, duckweed, black soldier fly) that might be generated on-farm at low cost. Two 30-day trials were conducted with six 200l aquaponic test units, for three replications of each treatment. At the time of writing, experimental trials were in progress.  The alternative aquafeed is expected to generate considerably lower concentrations of chemical effluents than the conventional feed and not to adversely affect plant productivity.