This work evaluated the effects of different carbon/nitrogen (C/N) ratios in the larvae and fry culture of Piaractus orinoquensis in biofloc system on the water quality, proximate analysis and growth performance. The experiment was conducted in two stages: (a) larval stage from 0 to 12 days post stocking (DPS) and (b) fry stage from 13 to 24 DPS, at a density of 10 larvae/L. Three groups of C/N ratios were evaluated as follows: T1: 10/1 ratio, T2: 15/1 ratio and T3: 20/1 ratio, each treatment with three replicates. Both in the larval and fry culture, total ammonia nitrogen (TAN) and nitrite were higher in the T2 and T3 treatments, while the nitrogen removal in T1 treatment was more efficient, resulting less TAN, nitrite and higher nitrate. However, the water quality parameters in all treatments were within the appropriate ranges for fish culture in biofloc. T2 treatment was nutritionally better, presenting higher levels of protein, lipids and energy. In both stages, P. orinoquensis survival and final weight were significantly higher in the T2 treatment. In conclusion, P. orinoquensis larvae and fry culture in biofloc is viable, improving the survival and growth at a C/N ratio of 15/1.