Molasses vinasse (MV) is rich in nutrients and has reuse value. Hence, it could be used to cultivate microalgae. In this study, Tribonema sp. GXU-A10 strain was cultured with MV and then added to Oreochromis niloticus feed. GXU-A10 removed 90.20 % and 80.95 % of TN and NH₄-N, respectively, from MV and achieved a biomass of 4.21 g/L. Adding 5 % or 10 % GXU-A10 significantly improved the WGR and SGR of O. niloticus (P < 0.05), reduced the accumulation of the lipid droplets in its liver, and facilitated the beneficial colonization of Bacteroidetes in the intestines of O. niloticus. To reduce the cost and ensure effectiveness, the recommended dosage of GXU-A10 is 3–5 % but not >10 %. These findings could promote the sustainable utilization of wastewater and microalgae resources and the development of aquatic feed additives.