Crystalpro white sand is calcium carbonate sand obtained from high purity natural minerals. It is produced for reef, marine and cichlid aquariums. It meets the calcium needs of corals, fish and invertebrates. Supports kh while maintaining the ph balance of the water. Does not contain brown iron oxide particles that harm living things and cause algae in other calcium sands. Due to its high purity, it does not cause silicate based diatom problem. Sieved 1-3 mm grain size which is ideal for bacterial cycle at the aquarium floor. It can be used without washing. It initially creates a temporary white cloud. For less turbidity, rinse the sand with water and lay to the aquarium floor.