Assessing plant growth, water quality and economic effects from application of a plant-based aquafeed in a recirculating aquaponic system

Aquaponics, the integrated production of fish and hydroponic crops in a recirculating system, is an intensive cultivation method in which metabolic fish wastes fertilize plants. This study compares the effects of two aquafeeds on Red amaranth (Amaranthus tricolor) productivity and on water quality parameters under cultivation of Blue tilapia (Oreochromis aureus), in three aquaponic replicate units per treatment over a 60-day experimental trial. The fishmeal-based control feed contains higher crude protein (40 %) and phosphorus (1.12 %) than the plant-based alternative feed (32 % and 0.40 %, respectively). The alternative feed resulted in a significantly higher amaranth crop yield (p < 0.05), with significantly lower concentrations of nitrate-N (NO3-N) and total dissolved solids (TDS) in the aquaponic culture water over the course of the experiment. Orthophosphate (PO4-P), total ammonia nitrogen (TAN), pH and dissolved oxygen (DO) levels were not significantly different between the control and alternative aquafeed treatments. Economic analysis revealed that improved plant productivity from the plant-based, lower-protein aquafeed may potentially increase total aquaponic farm revenue despite reduced fish production.