These beautiful stacks of River Rocks are a perfect complement to any fish tank, terrarium or fish bowl * the base is made of River Rock stacked with a decorative design * safe for saltwater and freshwater aquariums and terrariums * adds interest and natural beauty to your aquarium * great place for fish to hide and reduce stress. Rock Garden carries a broad selection of the finest decorative aquarium accessories including rocks (bowls, tunnels, stacks), plants and driftwood sculpture. Featuring both natural and cast resin rocks with decorative plants, they are a safe, healthy and eye-catching addition to any aquarium or terrarium.