The purpose of the present study was to evaluate the effects of three levels (30, 35 and 40%) of protein and two feeding rates (3 and 6%) and their interactions on growth of juvenile Calophysus macropterus. A total of 144 fish were cultured in tanks for a period of 90 days. Every fifteen days the weight and length of the fish were recorded. Growth in weight and length was determined; likewise, the productive indices: daily weight gain (GPD), weight variation coefficient (CVP), specific growth rate (TCE), apparent feed conversion ratio (ICAA), condition factor (K) and survival (S). The temperature (°C), dissolved oxygen (mg/L), pH (UI) and ammonium (mg/L) of the water in the fish tanks were monitored. The result of the t-student analysis showed that the evaluated feeding rates influenced (p<0.0001) the apparent feed conversion ratio, registering ICAA of 3.54±0.92 (3% rate) and 7.03±0.9...