We conducted rearing experiments in land-based nursery tanks, feeding artificial food to cultured juveniles Holothuria nobilis and H. scabra. Both species of sea cucumber were reared in floating cages supplied with seawater. The sea cucumbers grew fast in the experimental sections of the floating cage that contained beach sand, in which they were fed additional benthic diatoms. The maximum absolute daily growth rate for H. nobilis juveniles was 27.2 mg day^-1, and it was 291.5 mg day^-1 for H. scabra juveniles. That is, the absolute daily growth rate for H. scabra juveniles was approximately 10 times as great as that for H. nobilis juveniles. H. scabra juveniles grew from 3.8±2.3 g to 64.1±24.1 g in mean body weight in 322 days, and were not stunted when their density reached approximately 6,937 g m^-2. However, H. scabra juveniles did not grew to 500 g (commercial value size).