This study investigated the potential benefits of using Terminalia catappa leaf extract (TLE) as a natural feed additive in tilapia (Oreochromis niloticus) culture, exploring its effects on the fish. A 40-day feeding trial demonstrated that TLE-2% supplementation in the tilapia diet significantly enhanced growth performance and feed utilization efficiency. Phytochemical screening of aqueous, ethanol, and ethyl acetate leaf extracts revealed various secondary metabolites. GC-MS analysis of the ethanol extract identified bioactive compounds, including neophytadiene and squalene, which exhibited antimicrobial properties. The antibacterial activity of TLE was evaluated using the disc diffusion method, showing maximum zones of inhibition against Vibrio cholerae (18±1.5 mm). Analysis of digestive enzymes from the fish gut revealed increased activities of protease, amylase, and lipase, indicating improved digestive capacity. The results suggest that T. catappa leaf extract can be an effective natural feed additive to promote growth performance and digestive enzyme activity in tilapia. The findings in this study indicate that the TLE diet has a dual property of growth promoter and immunostimulant and can be a sustainable and cost-effective alternative to traditional aquaculture practices
