someone said there was a product in the lfs made for this, but i can't remember the name, i always use vinager, then wash really well with declored water a few times.
gl
mark
A razor blade would also work well. I got a paint scrapper and replaced the plastic edge with a utility razor blade and it lifts everything off my glass. Just be careful not to move it from side to side to avoid scratching up the tank.
I use a razor blade and then scrub with a wet rag and lots of table salt to get rid of any residue that the razor blade didn't remove. just with out when working close to the silicone in the corners. Oh yeah Don't hurt yourself !!!!!