T-Rex Bone Aid Calci-Sand is a pure, natural calcium carbonate, fine granular sand. It is an ideal substrate for reptiles, turtles, tortoises, and lizards. Reptiles like to eat their sand, therefore T-REX has designed this sand to be safe for both ingestion and digestion. The sand is a mineral substance and is safe for use with the heating elements, such as mats or cables. The sand also clumps readily when wet for easy detection and clean up of moist areas. It does not allow for mite infestation, mold or fungus growth which will keep your reptile healthy. It is made with colorants approved by the F.D.A. The amount of sand needed for your reptile's environment depends on how many valleys and hills you want to create. Generally, it is recommended that you fill the environment with 1-2" of sand depth