Innovative Marine - Magnetic Glass Cleaner
The Innovative Marine Magnetic Glass Cleaner is great for GLASS tanks up to 12mm thick.
Rivers to Reef says: We use this thing on our glass 210 gallon and it works well on scrubbing off algae in places we can get a larger magnet (its a little larger than a quarter). It even removes that stubborn green algae with a little effort. It is strong! They use Neodymium magnets in this thing, so keep it far away from anything you don't want exposed to a magnetic field. We once lost one of these for a day because it rolled off the counter and attached to a set of keys in somebody's pocket!