One of the aquaculture commodities with high economic value is grouper fish (Epinephelus sp.). RAS is known as one of superior and suitable aquaculture systems in juvenile fish culture. RAS installed with NBs is expected to increase the stocking density and production of hybrid brown-marbled grouper. This study aimed to analyze the system performance of grouper fish juvenile culture in high stocking density with water exchange system, RAS, and combination of RAS and NBs. This study used a factorial design with two factors, namely different stocking densities and cultivation systems. The densities were 500, 600 and 700 fish/m3, while the treatment systems were RAS without NBs, RAS installed with NBs, and control treatment with 200% water change. Each treatment was replicated three times. The total aquaria used for this study were 27 as each size was 1.5 m × 0.5 m × 0.5 m. The study results showed that the RAS installed with NBs and a stocking density of 600 fish/m2 showed the best results on fish production performance.
