Cement tub racks, 2 females per tub. I do have occasional issues with baby hoarding, but it doesn't normally result in any real issues. I tried a colony of 4 females in a larger enclosure, but I had a lot of issue with older babies pushing the younger ones out of the way and ended up with one female at the end trying to nurse like 35+ babies. I am seriously considering going down to one female per tub at least for a bit, as I normally produce more than I need and so I can see just who is producing what. Just don't thing they'll keep up once everyone is back on food.