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This study evaluated the effects of different feeding rates on the rearing of the curimba Prochilodus lineatus under biofloc (BFT) conditions. One hundred and sixty juvenile P. lineatus with average weights and lengths of 27.33 ± 2.07 g and 13.52 ± 0.16 cm, respectively, were randomly distributed in 16 experimental units (80 L) under BFT conditions and subjected to four feeding rates: 1.0%, 3.0%, 5.0%, and 8.0% of the fish biomass, for 60 days. During the assay, water quality variables and the proximate composition of the biofloc were monitored, as well as the productive performance and hematology of fish were evaluated. Compared to fish that received the diet at a rate of 1.0% of the biomass, the final length (14.47 ± 0.43 cm), final weight (35.55 ± 3.21 g), and gain in length (1.21 ± 0.34 cm) were significantly higher than those that received 5% of the biomass, while the fish that received 5.0% and 8.0% of the biomass, weight gain, and specific growth rate were significantly higher than those that received 1.0% of the biomass. Final biomass (296.89 ± 18.30 g) was significantly greater in fish that received the diet at a rate of 8.0% of the biomass than those that received 1.0% of the biomass (198.30 ± 49.36 g). The feed conversion rate (1.74 ± 0.26) was significantly lower in fish that received the diet at a rate of 5.0% than those that received 1.0% and 3.0% of the biomass. The protein efficiency (− 10.35 ± 5.37%) decreased significantly in fish in the 1.0% of the biomass. The survival rate of fish was significantly lower in fish from the 5.0% of the biomass (66.32 ± 14.03%) than in fish that received 3.0% of the biomass (100.00 ± 0.00%). The concentration of dissolved oxygen was significantly higher in the culture water of fish that received 1.0% and 3.0% of the biomass. The amount of sedimentable solids in the water was significantly higher in the culture water of fish at 8.0% of the biomass (242.50 ± 181.18) than in the groups of 1.0% and 3.0% of the biomass, while the hardness significantly decreased in the culture water of fish that received a diet at a rate of 5.0% of the biomass. Carbon dioxide was significantly greater in the water of the 3.0% of the biomass than in the 5.0% of the biomass. Regarding the proximal composition of the bioflocs, the dry matter significantly increased in the groups that were fed with a feeding rate of 8.0% (28.58 ± 0.01%), while the lowest contents were observed in the groups that received a feeding rate of 3.0% of the biomass. Crude protein was significantly lower in the groups that received a feeding rate of 1.0% of the biomass (28.94 ± 0.01%) than in the groups of 3.0% of the biomass. Ether extract was significantly greater in the groups of 8.0% of the biomass (1.62 ± 0.00%) than in the 3.0% of the biomass. Monocytes were significantly increased in fish that received a diet at a rate of 1.0% of the biomass compared to fish from the 5.0% and 8.0% of the biomass. Neutrophils were significantly increased in fish that received a diet at a rate of 5.0% of the biomass compared to fish in the 1.0% of the biomass. Hemoglobin was significantly decreased in fish that received a diet at a rate of 1.0% of the biomass. Hematocrit was significantly decreased in fish that received a diet at a rate of 1.0% and 8.0% of the biomass compared to fish from the 3.0% of the biomass. The results suggest that the cultivation of P. lineatus under biofloc conditions could be viable. Considering the productive performance, hematology, and water quality, a feeding rate of 5.0% of the biomass proved to be adequate for the experimental conditions adopted in the study. [ABSTRACT FROM AUTHOR]