This amazing scrubber is the last scrubber you'll ever need for your aquarium! The top is a coarse white scrubber that is good for glass surfaces and rough spots, breaking through the toughest of algae and grime. The bottom is a dual-layer thick sponge and melamine foam which cuts through really hard algae stains and also gets in the cracks and scratches, should you have any, and with almost no effort your glass is clean. These sponges are thick and designed to last a while and will be the only scrubber you'll need to make your aquarium sparkling clean! These can be used on glass and acrylic surfaces.