Nitrogenous compounds are among the main toxic substances that are produced in aquaculture systems, and their tolerance limits vary between species and their stages of development. In this study, in six bioassays, the acute toxicity (LC50-96h) of total ammonia nitrogen (TAN = NH3-N + NH4+-N), non-ionized ammonia (NH3-N), nitrite (NO2--N) and nitrate (NO3--N) to larval (0.05 ± 0.01 g) and juvenile (0.50 ± 0.3 g) Colossoma macropomum was evaluated. We used 0.5 L aquariums with 20 larvae and 30 L tanks with 10 juveniles, in triplicate, which were exposed to five concentrations of each compound and a control. The variables of water quality, mortality and behavioral changes of the animals were recorded for 96 hours. The estimated LC50-96h for larvae were: 6.00 (TAN), 0.17 (NH3-N), 3.77 (NO2--N) and 401.09 (NO3--N) mg.L−1 and for juveniles: 29.41 (TAN), 0.18 (NH3-N), 10.38 (NO2--N) and 1,948.00 (NO3--N) mg.L−1. Among the behavioral changes observed in the juveniles, lethargy, rapid and erratic swimming, breathing on the surface of the water, loss of balance and muscle spasms stood out. The results show the high tolerance of tambaqui to nitrogen compounds in aquaculture systems.