The present investigation evaluated the effects of three stocking densities of postlarvae (pl) of paco Piaractus brachypomus (Cuvier, 1818) 10 days after the hatching of the DPE, in an aquaculture recirculation system (RAS), for 35 days. The investigation consisted of 3 treatments and 3 repetitions (T1: 1pl / liter, T2: 3pl / liter and T3: 5pl / liter), distributed in a completely randomized design (DCA). The food was constituted in 2 stages: 1st stage: Live food + Commercial food + Additive; 2nd stage: Commercial feed + Additive, from which the growth in weight and length, the zootechnical indices and the water quality parameters are evaluated. Growth was recorded every 17 days, parameters such as temperature, pH, dissolved oxygen and oxygen saturation were analyzed daily, while alkalinity, ammonia, nitrites and nitrates were analyzed weekly. The results indicate that in the growth of w...