The management of the first feeding is a critical stage in the viability of the larvae and fingerling rearing. So far, the first feeding of the bryconids record the best results when fed with forage larvae; thus, the aim was to evaluate two species of cladocerans as live prey in the first feeding of dorada Brycon sinuensis and to evaluate their effects on the control of cannibalism. Larvae (1.2 ± 0.15 mg and 5.9 ± 0.4 mm initial weight and total length) were fed Moina minuta (Mm), Macrothrix elegans (Me) or a mixture (50:50) of cladocerans (Mix) at a rate of 20 prey mL⁻¹, once for 24 h. Another dorada larvae group were fed newly hatched larvae of Piaractus brachypomus (4.5 ± 0.9 mm) as forage larvae (F_L) in a ratio of 2:1 (prey:predator). The larvae were stocked to 50 L⁻¹ in aquaria with 5 L of useful volume (12 per treatment). The growth, survival, stress resistance, cannibalism mortality, and the number of prey in the gut contents were analyzed. Dorada larvae fed F_L showed higher growth, but those fed Mm showed the highest survival rate (76.1 ± 6.6%) and the lowest cannibalism mortality (16.8 ± 3.7%) (p < 0.05). The use of the cladocerans allowed high survival and stress resistance (95.3 ± 2.4%), and M. minuta proved to be a suitable prey for cannibalism control in the management of the first feeding of dorada larvae.

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.