Cyclotella menegheniana is a diatom microalga often found in both marine and freshwater environments, characterized by a high-quality nutritional profile, including fatty acids, protein, and carotenoids, it is also a promising bioresource for improving food and animal feed nutrition. In this study, two separate experiments were conducted. In the first experiment, the utility of including C. menegheniana in the diet was evaluated for its impact on the reproductive efficiency, hematobiochemical biomarkers, and oxidative enzymes of broodstock Nile tilapia, Oreochromis niloticus, fish fed diet T2 (with 10 g kg−1 C. menegheniana supplementation) recorded the highest (P ≤ 0.05) gonadosomatic index (GSI) for female tilapia, whereas fish fed diet T3 (with 15 g kg−1 C. menegheniana supplementation) recorded significantly higher (P ≤ 0.05) values of egg diameter, egg volume, sperm motility, and sperm concentration …