Stocking density is well known as an important field in aquaculture. Although many studies on stocking density have been conducted, however effects of rearing grouper (Epinephelus coioides) with different densities in recirculation and flow-through system are not well known. In this study, grouper juveniles (14.22 ± 0.67 g) were reared into 100-L aquaria at 15, 20 and 25 fish/aquaria and cultivated for 70 days. Statistical analyses showed that the highest growth performances observed in group

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... ared at high densities (25 fish/aquaria) in recirculation system (R25), with an average final body weight and length were 95.82 ± 4.24 g and 18.72 ± 1.40 cm, respectively. Significant increase in weight gain and specific growth rate and decrease in food conversion ratio were observed in R25 after 10 weeks. However, no statistically significant different was found in survival rate and condition factor in all treatments. This study found that the effects of stocking density on growth and feeding ratio were higher in recirculation system compared with flow-through system. Further analysis determined that high stocking density in recirculation system and medium density in flow-through could affect the growth, feeding and fish behavior of this species.