Bath Bombs/bubble bars and Tub damage

[xaceswildx]

I read on here awhile back about certain bubble bars and bath bombs staining/ruining bathtubs. My bf and I just got a new house with a nice new tub in it so I can finally start using bath goodies... but I want to know which ones to stay away from.

I searched for a bit and can't really find anything about this (if I missed it, I'm sorry!)