Seachem DuoPad Non-Scratch Dual Surface Alge Pad for Glass & Acrylic Aquariums 

The Seachem DuoPad is a non-scratch, dual surface algae pad for glass & acrylic. The melamine foam side uses micro abrasive technology to easily remove algae from the sides of your aquarium, while the durable scrubbing side allows you to attack the rougher grooves of rocks and driftwood. It is particularly effective at removing algae from scratches. It is chemically inert and does not use soaps or detergents. It's white color contrasts against dark algae making it easier to see when areas are fully clean.