So I'm kind of pissed off because about a month ago some substrate got caught inbetween my mag float and put a couple nasty surface scratches on my tank. I can't feel them, but 3hrs of buffing with cerium oxide barely took out the scratches. I got some 2000 grit sand paper and buffed for about an hour and they were noticeably lighter but still aren't gone. I have some 600, 800, 1000, 1200, and 1500 grit coming in from ebay to finish off the job. The real reason I'm making this post though is that I noticed that buffing with 2,000 grit didn't add any visual scratches to the glass, so for the past week I've been cleaning my aquarium glass with a piece of 3,000 grit sand paper sandwiched between my mag float. I can SLOWLY move tha mag float across the surface of my glass and remoce ALL of the debris in 10 minutes (I don't have to circle 20 times in the same spot to get rid of hard algae spots). I just thought others might be interested in trying this out if they're having trouble with glass algae. I can even get into really tight corners using this method. I suggest trying it in a corner of your tank first to make sure it won't damage your glass. Mine is tempered and there's no effect.