Help! My rats keep chewing through my tubs!

I plan on changing to cement mixer tubs in the next couple of weeks (it is coming into finals week for me in vet school, so I am a little busy!). I will post a picture of the rack once I get them all installed. Thanks for all the help. I also plan on culling the chewers once I wean off their current litters. The babies will also be fed to get rid of that line of genetics.

The babies may be OK to keep actually, provided the parents don't teach them to chew before they are weaned. This could be a way to re-start your colony without having to buy new rats.

I found that even with the cement tub racks, a chewer will find the hole in the end of the tub (presumably to hang on a nail) and they will use that as the starting point to chew through the concrete tubs. I started making a little home made solution in my cement tubs using a nut, bolt, two washers and a small piece of hardware cloth and haven't had a single issue since. I can try to post a pic later if you'd like...

I pop-rivet a piece of aluminum flashing over that hole after trimming off the little raised portion around the hole. I have started doing this to all the mortar tubs when I start using them. Seems like if I don't, it will go for months without an issue, then I come down to find wood and plastic shavings in a pile with, hopefully, a couple rats staring out a hole at me. Otherwise, it's an empty tub with a hole and I now have to locate it's former occupants.