Water quality, growth, and hematology in Nile tilapia cultured in biofloc systems using molasses as a carbon source

Biofloc technology represents a sustainable solution for aquaculture development, articularly in regions with limited water resources. We hypothesized that the addition of molasses to biofloc systems, at different carbon-to-nitrogen (C:N) ratios, could modulate hematological responses in Nile tilapia (Oreochromis niloticus), potentially occurring prior to detectable effects on growth performance. Therefore, this study evaluated the effects of molasses supplementation at C:N ratios of 10:1 (10M) and 20:1 (20M), compared to a control without carbon addition (0M), on water quality, growth, and hematological parameters in juvenile tilapia reared in 12,800 L tanks (stocking density: 50 fish/m³) for 107 days in a semi-arid region of Brazil. Results showed that C:N ratios significantly altered the water's physical and chemical properties. However, final productivity (14.5 ± 1.0 kg/m³) and survival rate (95.9 ± 1.4%) were not affected. Notably, molasses supplementation reduced albumin levels while increasing total plasma protein and globulin concentrations, indicating a positive modulation of the fish immune response. These findings suggest that carbon addition in biofloc systems can improve water quality and promote early immunophysiological responses in Nile tilapia under semi-arid conditions.