Caribsea South Sea Base Rock for AquariumsNatural weathering processes form the fantastic shapes of CaribSea South Seas Base Rock by the erosion and pitting of limestone over the course of eons. It is clean and safe for marine, reef and hard water freshwater aquariums such as African cichlids. South Seas Base Rock can also be an interesting and realistic addition to a desert reptile biome. At an unprecedented 50% void space (macro and micro) Safe for all marine and high ph freshwater systems