Colossoma macropomum is one of the fisheries commodities that has high economic value. It is necessary to to use quality feed, such as maggot, to increase its production. Since fish growth is largely influenced by nutrient content in feed and fish energy needs Maggot has high protein content of 40-50% and fat content 29-32%.This study aimed to determine the retention of protein and retention of Colossomamacropomum. This study used an experimental method with a Completely Randomized Design consisting five treatments and four replications. The provided treatment was a commercial feed which was replaced by the maggot fermentation with different doses. The treatments used in this study were: treatment P0 (0%), P1 (12%), P2 (14%), P3 (16%) and P4 (18%). Parameters observed in this study were protein retention and energy retention. This research used Variant Of Analysis (ANOVA) for data analysis. The result showed that the substitution of maggot fermentation flour on commercial feed for 30 days of maintenance was significantly different (p<0,05) on protein retention. While the energy retention, result showed no significantly different (p> 0.05). The protein retention value of Colossoma macropomum’s meat was 7.8568% -10.3620% and the energy retention showed 3.9868% -5.2540%.