Use the special biOrb cleaning cloths to effectively remove algae without scratching the bowl. Available in packs of three these special cleaning cloths have a smooth side for regular cleaning and a rough side for really tough algae marks The rough side can also be used to remove lime scale build up from the base of the light unit. biOrb Cleaning pads should only be used on the inside of the aquarium. Reef One do not recommend using other algae pads on the biOrb as these may scratch the acrylic.