Our CongaRoc Aquarium Gravel is available in Crushed Rock, Agates and Water-Worn Pebbles. Gravels are inert and free of chemical activity. Our product has been screened and washed prior to our coating process, making CongaRoc the cleanest aquarium gravel available. There is no need to rinse prior to use. The key to every successful aquarium is water quality. CongaRoc was specifically developed to provide a safe, non-toxic biological filtration medium for freshwater and marine environments. Using our exclusive, non-epoxy process, our gravel will not change water chemistry or leach harmful contaminants into water or soils.