I use the Tom Aquatics 3 in 1 scraper - it has attachments for a scraper, a scrubber, and a shovel that's useful when the &*%($!ing maroon clownfish knocks over a rock. The metal scrapers can be purchased separately for $2.50, and I get a new one every couple of months to keep them sharp.
As for the mag-float...yes, you should be using the 300 model, not the 125. The 125 is supposed to be rated for up to 3/8" glass, but even at that size it's delicate. I use a 125 for my 37g tank (1/4" glass) and a 300 for my 110g tank (1/2" glass). A trick I read on these boards that makes sense is that you shouldn't keep the scrubber always connected on the glass - the constant pressure between the magnets will eventually flatten out the little nylon bristles and make them less effective. The guy who mentioned this suggested you keep the parts separate outside the tank until you need it. Too late for me, but maybe you could give it a try and tell us if it's true.
