Natural Tufa rock that is perfect for almost any type of aquarium, terrarium, or reptile tank. Works well in both fresh and saltwater aquariums and is completely safe for all animals. Each rock is truly unique. The average piece of Lg Tufa rock is 8″x 8″ to 8″x10″. Naturally-textured rocks add depth and design. Completely Natural Tufa Rock Stone For Use In Fresh Water And Marine Aquariums – Will Not Buffer pH. Sold by the piece.