Environmental Sustainability of Nile Tilapia Reared in Biofloc Technology (BFT) System: Evaluation of Carbon, Nitrogen, and Phosphorus Dynamics and Indicators of Sustainability

This study aimed to evaluate the dynamics of total carbon (TC), total nitrogen (TN), total phosphorus (TP), and some indicators of environmental sustainability of Nile tilapia reared in a biofloc technology (BFT) system. Nile tilapia fingerlings were cultured in three BFT units of production (4.2 m3 each) at a stocking density of 395 fish/m3. After 70 days, the survival rate was 98.05%, with a final average weight of 20.43 g, and apparent feed conversion of 1.05. Nutrient inputs were from supply water, initial fish biomass, and feed; outputs were measured from the final fish biomass and effluent. TC, TN, and TP concentrations in the water increased linearly over time (p < 0.001) by 1.54, 1.66, and 0.44 mg/L, respectively. Feed contributed over 88% of nutrient inputs, while fish final biomass accounted for over 50% of output. Nutrient retention in fish final biomass was 29.74% (TC), 45.38% (TN), and 46.34% (TP). The system had low eutrophication potential, estimated at 57.39 kg TC, 20.02 kg TN, and 5.70 kg TP per ton of fish. Water use was 135.3 m3/ton, but energy demand was high (114.59 MJ/kg). The closed system reduces biodiversity risks by preventing fish escape. In conclusion, BFT supports high fish productivity with efficient nutrient use, minimal water use, and limited environmental impact, contributing to environmentally sustainable aquaculture.