Safe for use in both freshwater and saltwater tanks, the Aqua Life scrubber pad is designed to remove algae and hard water deposits from your glass tank or aquarium. Use this product with glass tanks only for best results and to avoid scratching. MADE FOR ALGAE REMOVAL: made for algae and hard water deposit removals, this scrubber pad is perfect for all of your aquarium maintenance needs. USE FOR GLASS TANKS ONLY: while this product is safe for use in both freshwater and marine water, this scrubber pad is designed for glass tanks. Other tanks require specialized scrubber pads, which are available, sold separately. Available Size: 3 x 4"