I used isopropyl 91% alcohol. The tank wasn't warm at all - just room temp. Not only did it crack all over the place, the tank walls turned completely white; they look like I spray painted them white. Very weird. Not sure if rubbing alcohol is less potent, but I'd be afraid to try either at this point. If this happens again, I think I'll just do the 1:19 bleach, rinse like crazy, declorinate and then hope for the best.