Blue Treasure Coral Sand is taken from the pollution-free island in south sea of China,no phosphate,nitrate and surface contaminants.Coral Sand is with natural porous,it is suited to be as bottom sand filter in aquarium tank owing to its big surface area,it can simulate river bed and seabeach in addition it can grow beneficial bacteria as well.The main content of the coral sand is calcium carbonate,which can be conducive to the stability of PH value in seawater.