, growth, and survival of juvenile sea cucumber during a 30 d feeding trial. Animals were fed one of four diets in which 0, 10%, 15% or 20% of the carbon source was replaced with sucrose. Additionally, we tested the effect of water-exchange frequency (3 or 7 d). The experiment was set up using an orthogonal design and we measured growth performance, survival, enzyme activities, and soluble protein content. The activities of amylase(AMS) in the experimental groups were generally higher than in the control, indicating that the bioflocs stimulate amylase activity in . On day 15, superoxide dismutase(SOD, 32.9 U/mg prot)and alkaline phosphatase (AKP, 146.8 U/g prot)activity was higher in the 3 d/15% group than in the other three groups and the control( Similarly, SOD (35.3U/mg prot) and AKP(158.8 U/g prot) activity was higher in the7 d/20% group than in the other three groups and the control group( AMS and SOD activity were higher on day 30 than on day 15 in the 7 d/10% group and the increase in AKP activity was particularly significant. The growth rate (4.12%/d) and survival (98.9%) were highest in this group, whereas survival was lowest (91.8%) in the 3 d/20% group. Furthermore, the soluble protein content in the body wall of was not different from the other three groups and the control ( was higher in the 7 d/ 15% group than in the control(<0.05), but was not different from the 7 d/10% group. Thus, our results suggest that areduction inwater exchanging frequency and feeding quantity may be beneficial to growth performance and soluble protein accumulation in . Our results provide a basis for feeding quantity and water-exchanging frequency for juvenile sea cucumber in biofloc technology systems.