CaribSea South Seas Base Rock (10 lb) – Natural calcium carbonate rock pieces perfect for building the foundation of reef aquariums or hardscape for African cichlid tanks. These dry rocks feature interesting textures and holes, providing lots of surface area for beneficial bacteria and hiding spots for fish. South Seas Base Rock is free of any organic matter or pests, making it a safe start for new setups. Over time, it becomes live rock as it’s colonized by microorganisms and algae, helping stabilize water chemistry and creating a realistic ocean reef appearance.