Effect of bioremediation on water quality in an aquaponic system with koi carp and lettuce

Aquaponics is a system that integrates aquaculture and hydroponics, promoting the reuse of waste from aquaculture effluents, the production of high-quality food, and the reduction of environmental impact. The objective of this study was to evaluate the effect of three substrates (peat, gravel, and rice hulls) on the bioremediation of water quality and the yield of curly lettuce (Lactuca sativa) within an aquaponic system with koi carp (Cyprinus carpio). The experiment was conducted at the Botana Experimental Farm (Pasto, Colombia) using a recirculating aquaculture system installed in a tunnel greenhouse. Physicochemical parameters of the water and the removal efficiency of solids, organic matter (BOD₅ and COD), and nitrogen compounds (NH4+, NO2-, NO3-) were monitored, in addition to crop yield. The results obtained showed that the physicochemical conditions remained within optimal ranges during the experimental period. No significant differences were found between substrates in the removal of solids, organic matter, or nitrogen compounds (p > 0.05), indicating that bioremediation was primarily associated with the biofilter and the system's operating conditions. In contrast, lettuce yield was significantly higher in peat (3.69 kg/m²) and gravel (3.63 kg/m²) compared to rice hulls (2.53 kg/m²), demonstrating that the substrate influences the productive response of the vegetables. It is concluded that aquaponics has become established as an environmentally sustainable alternative for water bioremediation and the production of value-added foods.