Black Soldier Fly (Hermetia illucens) larvae oil in diet: Effects of growth, feed utilization; whole-body fatty acid and amino acid profile; immunology responses and Body Coloration of Goldfish Goldfish (Carassius auratus)

Abstract This study evaluated the efficacy of Black Soldier Fly larvae oil (BSFO) as a sustainable substitute for traditional fish oil in the diets of goldfish ( Carassius auratus ). To determine the ideal inclusion rate, a comprehensive 49-day feeding trial was conducted, evaluating six distinct BSFO replacement levels ranging from 0% to 30%. The results demonstrated that incorporating dietary BSFO significantly improved overall growth performance and feed efficiency metrics. Specifically, the 30% BSFO replacement level emerged as the optimal formulation. It successfully maximized the specific growth rate (reaching 1.14% per day), total weight gain, and feed utilization, while simultaneously minimizing the feed conversion ratio. Furthermore, this 30% inclusion level effectively enriched the whole-body essential amino and fatty acid profiles. It also maintained normal hematological parameters, supported healthy immunological responses, and visibly enhanced integumentary carotenoid pigmentation. Conclusively, a 30% BSFO substitution safely improves the growth, nutritional quality, and overall aesthetics in ornamental aquaculture.