Carisea Life Rock are safe for all fish and invertebrates, aragonically based (does not contain cement), require no hardening and are impregnated with live bacteria and spores. Once placed in the water, the dormant bacteria will come to life and begin to colonize: this will speed up the cyclic process. CaribSea Life Rock is colored to simulate true coralline algae. So you do not need to wait 6 to 8 months before the coralline algae grow to have a mature looking aquarium.