Seachem Algae Pads are made of melamine foam and are safe for use on glass and acylic tanks. Bulk and single algae pads are 15mm thick while the algae pads in the 3 pack are 25mm thick, which means they last longer. The DuoPad has a melamine pad on one side and an acrylic safe scrub pad on the other. The scrub pad can take care of the ease to remove algae, while the other side can take care of the harder to remove stuff.
Rivers to Reef says: These things really work. We were skeptical initially, but after trying them out work wonderfully, especially on acrylic where metal scrapers are forbidden and plastic scrapers only half work. These pads also work wonderfully on getting water deposits off of your light fixtures and the outside of your tank.