Yep, I foster all the time. I have three breeder groups, and I sort my babies out by pinkies, fuzzies, and pups (each size in a different breeder group). I tend to sort since often times if a new mom has babies in with pups, the pups push the pinks down to the bottom and they can't get any milk. Of course, I house my breeders together all the time too (yes, including the male). Some people have said that the males will kill any babies that are not theirs, but I've never had any issues with this--if I'm adding new pinks to a tub, I handle all of the babies so they all smell the same, and the males have not killed any to my knowledge. I have found a few dead babies on occasion, but that comes with the territory--not all babies survive.