Effects of Different Organic Carbon Sources on Water Quality and Growth of Mugil cephalus Cultured in Biofloc Technology Systems

The addition of organic carbon sources in biofloc technology (BFT) systems promotes microbial community development, enhancing water quality, nutrient recycling, and supplemental feeding through microbial biomass. These characteristics make BFT a viable strategy for the cultivation of promising aquaculture species, such as Mugil cephalus. This study evaluated the effects of three carbon sources—unrefined cane sugar (locally known as chancaca), refined sucrose, and beet molasses—on water quality and growth performance of M. cephalus juveniles reared in a BFT system. Juvenile mullets (4.33 ± 2.09 g) were cultured for 45 days at a stocking density of 0.03 ± 0.01 kg·m−3, with biofloc pre-matured in ex situ tanks. Most water quality parameters showed no significant differences among treatments (p > 0.05), except for nitrite concentrations, which were significantly higher in the sucrose group (p < 0.05). The highest growth performance was observed in the sucrose treatment, with a weight gain (WG) of 4.26 ± 0.51 g, an average daily weight gain (AWG) of 0.09 ± 0.01 g, and a thermal growth coefficient (GF3) of 1.27 ± 0.15 at a constant temperature of 24 °C. Bromatological analysis of bioflocs revealed significantly higher crude protein (CP: 9.8%) and energy content (Kcal·100 g−1: 3.44 ± 0.2) in the sucrose treatment compared to chancaca (CP: 5.1%). These findings confirm that M. cephalus can be effectively cultured in BFT systems using simple carbon sources. Refined sucrose, due to its high solubility and nutritional contribution to biofloc formation, is recommended for improving growth performance and system efficiency in M. cephalus production.