I think your safer with the CLR. As I've heard of this being used, I think it was on 50 gal build by clownonfire. That compound would leave a residue on the tank right, like your buffing away flaws and bonding the compound into the glass, I would just do the outside. Try a magic eraser, it removes 50 year old gummy stuff that gathers on antiques, where I'd used everyhibg in the house to get it off.