Anyone ever had any luck with removing hard water stains? I have a 180 I bought from a guy and come to find out, he let the water level in the tank get low and therefore hard water stains appear so far to be permanent around the tank. It's very annoying. I called my LFS and he said that there's no way to get them out, even with CLR. He said to try razor blade, tried it and didn't work. Any ideas?