I just put together one of the racks from Tierney Reptiles sold...Very nice by the way and easy for the busy person who doesn't have time to make them from scratch...

But my question is, "Do rats normally chew through the cement tubs?" I have two tubs so far chewed through by the rats. If my son didn't find their heads peeking through, I would of had small colonies roaming my basement. Is this normal? Is there anything that can be done to deter them from chewing through?