Recommend to be used on aquariums up to 30 gallons with a surface thickness up to 3/16”. Product dimensions: (2 3/8” x 1 3/8” x 1”). Easy removal of algae from glass/acrylic surfaces. No longer knock over decorations, damage corals and invertebrates. No longer get your hands submerged into the water of the fish tank. Time/money saver on maintenance. Large cleaning surface area makes the job quick and efficient. Stays free of debris. Can be maintained attached to aquarium surface. Strong, high-quality neodymium rare earth magnets. Can be used on freshwater and saltwater tanks. Magnet does not lose strength over time. Easy retrieval of inner magnet