Mag-Float-30 Small Glass Aquarium Cleaner (w/ scraper option) Recommended for use with glass aquariums up to 30 gallons with a surface thickness up to 3/16. Features scraper attachment option (Scraper Blade sold separately). Product dimensions: (2 3/8 x 1 3/8 x 1). The Mag-Float floats when the inner magnet separates from the outer magnet. Magnet does not lose strength over time