The sea cucumber, Holothuria scabra (sandfish), is an important aquaculture species due to its high economic value. This has led to over-exploitation causing population decline; consequently, aquaculture of sea cucumber is required to increase production. This study aims to obtain data and information on the growth performance of sandfish reared in a sea pen culture system and develop its cultivation in coastal areas of Sumberkima Village, Gerokgak District of Buleleng, Bali-Indonesia. Three 10 x 5 m² sea pens (KJT), namely KJT-A, KJT-B, and KJT-C, with a 3-m height net, were installed at the site using bamboo and plugged into the seabed to support the net. These three KJTs have different seafloor characteristics from the experimental group. The sediment composition in the KJT-B consisted of loamy sand with high organic matter compared to KJT-A and KJT-C, which were sandy. The sandfish juveniles were stocked into each KJT at a density of 300 individual/pen with an average initial weight of 17.7±6.6 g and an average total length of 6.6±1.2 cm for 180 days. The results showed the daily growth rate of sandfish in KJT-B was the highest (1.44 %/day) when compared with KJT-A (0.92 %/day), and KJT-C (0.96 %/day). These results indicated that the growth of sandfish (H. scabra) depends on the structure and composition of the seafloor sediment. The seafloor sediment structures of loamy sand with high organic matter and C-organic content promote the best growth of sandfish.