Adding a small amount of the fruit powder Phyllanthus emblica (also called amla) to tilapia feed helped the fish grow faster and increased the activity of the growth hormone IGF‑1 gene. A higher amount of the powder didn’t boost growth as much but did improve the fish’s immune system and antioxidant defenses. The study shows that the dose matters: low‑dose for growth, higher‑dose for health protection.

Identifying natural growth-promoting agents and implementing environmentally sustainable methodologies are paramount strategies for enhancing the performance and welfare of aquatic fish farms. Phyllanthus emblica (PE) possesses a broad spectrum of bioactive properties, including antioxidant, antiviral, antimicrobial, and immunomodulatory effects. Hence, this study aimed to investigate the beneficial effects of PE dietary supplementation on the growth, immunity, redox homeostasis, organ histology, gene transcripts, and disease resistance of Red Tilapia against Fusarium oxysporum. A total of 240 fish (25.0 ± 3.0 g) were randomly distributed among 12 ponds, with 20 fish per pond. The fish were fed a basal diet supplemented with 0 (PE0), 5 (PE5), 10 (PE10), or 20 g of PE powder per kg of diet for 70 days. Following the trial, a challenge test was carried out. The PE5 group achieved significantly greater body weight, weight gain, specific growth rate (SGR) and digestive enzymes (lipase and amylases) than the PE20 group (p < 0.05). However, the PE5 group recorded the best feed conversion ratio compared to the other groups (p < 0.05). All PE-supplemented groups exhibited lower muscle lipid content and higher ash content (p < 0.05). PE-fortified groups displayed substantially lower levels of liver enzymes (AST, ALT, and ALP), creatinine, glucose, and lipid profile (cholesterol, triglycerides) compared to the PE0 group (p < 0.05). PE-fortified diets significantly enhanced the fish's antioxidant enzyme activities (SOD, CAT, and GPx), immunological parameters (p < 0.05) for phagocytic activity, phagocytic index, and WBCs) and preserved the intestinal and hepatic tissues. The supplementation of 5 g PE/kg in Red Tilapia significantly enhanced the gene expression of growth genes (GH and IGF-1). In contrast, the group supplemented with 20 g PE/kg showed superior results for immune-related genes (including CC chemokines and interleukin-8) and antioxidant enzymes (SOD and GPx) (p < 0.05). Overall, the inclusion of 5 g/kg PE optimized growth performance in Red Tilapia, while the inclusion of 20 g/kg resulted in superior immune and antioxidant capabilities. These results highlight PE's dual potential to enhance growth and boost health, confirming its promise as a natural feed additive for sustainable Tilapia aquaculture.