The Mag-Float revolutionary patented floating aquarium cleaner removes algae from your aquarium without getting your hands wet. This super-convenient floating cleaner polishes aquarium surfaces and floats when the inner magnet separates from the outer magnet. Because you never have to reach into the aquarium, not only can you stay clean and dry, but you can also avoid introducing toxic soap or lotion residue from your hands into your aquarium. The Mag-Float's powerful rare earth neodymium magnets provide a lifetime durability and ample strength to get the job done. Simply move the outside magnet that contains the felt, and the inside abrasive velcro magnet scrubber follows; cleaning as it goes! If the magnets separate, the inner magnet floats right to the water's surface for easy retrieval. Great for both freshwater and saltwater aquariums. The Large size glass aquarium cleaner is recommended for use on aquariums up to 350 gallons, with a surface thickness up to 5/8".