Saim Aquarium Algae Cleaning Magnet Glass Aquarium Cleaner, Large This magnetic cleaner can be used on glass or acrylic tanks up to 0.20" - 0.79" (5 - 20 mm) thickness Perfect design that flips from scrubber to scraper. Complete cleaning without using extra hand. Blades can be assembled easily.The plastic blade is suitable for acrylic tanks ,and the stailess steel blade Use only on glass tanks