Comparison Between Environmentally Friendly Recirculation Systems with Biofilter, Green Water, Bioflocs, and Partial Water Exchange in the Cultivation of Nile Tilapia

With the intensification of aquaculture, sustainable farming systems are essential for the rational use of water. This study compared four rearing systems for juvenile Oreochromis niloticus: biofilter-based recirculation, green water, biofloc, and a partial water-exchange control, evaluating their effects on water quality and growth performance. Ninety-six juveniles (2.48 g) were stocked in sixteen 100-L aerated aquaria (four replicates per system) and reared for 60 days under controlled temperature. Water-quality variables and growth indices were analyzed using one-way ANOVA (P<0.05). The recirculation system provided significantly higher water hardness and calcium concentration than the other systems, as well as higher alkalinity than the control and green water systems, while maintaining nitrogenous compounds within safe limits. Fish reared in the recirculation and biofloc systems exhibited greater final weight, weight gain, specific growth rate, and an improved feed-conversion ratio compared to the control. The green-water system produced intermediate and non-significant responses. Survival, morphometric indices, salinity stress tolerance, and skin color parameters did not differ among treatments. Overall, the recirculation and biofloc systems improved the performance of juvenile tilapia under intensive rearing conditions, with the recirculation system providing better physicochemical water conditions and buffering capacity, making it the most robust and culture-efficient option..