Culture practice of Oreochromis niloticus through recirculating aquaculture system (RAS): a modern and growth-optimized approach of fish culture by maintaining water quality with proper fish stocking density in Bangladesh

The recirculating aquaculture system is a modern method for managing indoor fish culture and ensuring maximum output. The focus of this research was to see how water physical and chemical characteristics influenced the productivity of tilapia in fish tanks (size: dia-3.35 m and depth-1.5 m) of constant water capacity (10,000 l) using three stocking densities such as 1200 fish/tank (89 fish per m3), 1000 fish/tank (74 fish per m3), and 800 fish/tank (59 fish per m3) in Treatments I, II, and III, respectively. Ninety fish samples were randomly obtained every 2 weeks over 4 months; they were weighed, measured, and returned to the tank. The average range of different physical–chemical parameters was within the limit, with some variations observed in certain readings. It was noted how much weight the fish gained on average and their specific growth rates (SGR) for Treatments I, II, and III at the end of the experiment. The treatments indicated statistically substantial differences (P<0.05) considering the specific growth rate, final mean weight, and weight gain. Treatment III which was the controlled group had a significantly higher SGR than the other treatments. Correlation between length, weight, specific growth rate (based on weight), and physical–chemical parameters was observed and tabulated. The regression between fish growth and physical–chemical parameters was also calculated. The results of this study consistently indicate that stocking density is a more important factor in determining the overall yield than water quality indicators in RAS. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.