I've thought the same thing about CLR. On the tv ads they use it for a variety of things like cleaning out the coffee pot. If it would be safe for aquarium use.....not sure. I figure give it a really go rinse afterwards you might be good to go.

Not sure if Lime Away would work or not either. If I see a Lime Away ad showing them cleaning a coffee pot, I'd consider it.........but that stuff seems a little to potent for me to take the risk.