I culled the chewers and haven't had an issue for a long time.

I do provide stuff for them on a regular basis. I save toilet paper tubes and paper towel tubes and put treats and food inside and pinch the ends shut. I also use paper and put treats in the middle, then wad it into a ball. Giving them treats on a regular basis, or chew things like the hard doggy bones or sometimes even real bones. They entertain themselves just fine, but I like giving them things anyway. It's not like I'm spending much money on it and it surely can't hurt to give them extras.

I've watched the pups roll around with a wad of paper for an hour playing. They're very entertaining.

The best breeders will almost always come from a feeder/breeder. They are breeding for healthy, fast growing, high producing animals. Pet breeders do not concentrate on fast growing or high producing. Pet stores often have rats from the same suppliers that produce feeders, so if they are healthy looking rats, you can buy from pet stores, but they usually don't have young ones.

If you have rats in a rack system, and the temps drop super low, you can cover the top of the wire for 2/3 of the tub size and the rats will still stay quite warm. A little extra bedding and they'll be fine without extra heat. Heat on the other hand is a killer. A fan in the room and keeping things clean helps.