Coral Bone Gravel is coral or shell fragments that can continuously enrich aquarium water with calcium carbonate. Because of its alkaline content, through its filtered pH is generally 7.0 ~ 8.5, the release of calcium ions, magnesium ions to the sea or freshwater, provides a higher hardness and pH stability for aquarium biological surviving. Due to its rich pore structure, as a biological filtration system carrier, a large number of nitrifying bacteria can be breed in it. Suitable for freshwater, tropical and salt water marine reef aquariums.