Safe for Both Glass and Acrylic Tanks! * Patent pending design allows you to use any old credit card, gift card, hotel room key etc as a scraper blade....you may never have to buy blades again! * Blade cards can be inserted in any direction for multiple levels of flexibility * Cut your own custom blade card shapes for cleaning difficult curved or tight areas of your tank. * Solid fiberglass matrix handle is practically indestructible! * Optional stainless steel blade (sold separately) is great for tackling really hard algae deposits all over your tank (for glass tanks only). * Replacement acrylic blades are available as well. Check out a review from BRStv: