The Seachem Algae Pads (3 Pack) are non-scratch algae pads for glass & acrylic. The melamine foam uses micro abrasive technology to easily remove algae from the sides of your aquarium. They are particularly effective at removing algae from scratches. They are chemically inert and does not use soaps or detergents. Their white color contrasts against dark algae making it easier to see when areas are fully clean. 4.5" x 2.5" 25 mm Thick 3 Pack