Personally, I isolate a female in the last week of pregnancy in a cage by herself, with nesting material. I don't put her and the pups with any other rat again until the pups are about two weeks old. I keep my females in groups of three, take one out to keep with a male for a week, put her back in, then take her out when she's about to give birth and put her in a different cage. I also keep my rats in tubs, rather than tanks - I do have a tank, and I plan on phasing it out to replace all the tubs and tank with a rat rack, as soon as I get one built. I made the mistake of breeding all my females at once, when I started... now I'm doing one at a time, with a six week break between weaning a litter and being bred again for each female, so they can recover and fatten up some before the next litter.

Unfortunately, it looks like I'm going to have to go back to breeding mice. Ugh. I do not like breeding mice. They stink MUCH worse than rats do.