Right now I have 12 tubs with 1.3 rats in each tub. They are the concrete mixing tubs you get from lowes. and I have one of the larger tubs set up with 1.5 rats. So I have 41 breeding females total right now. My production seems to be pretty low doing it this way so I'm thinking of building a rack mabey 20 tubs or so to seperate the females in to when they swell up a week or so before they give birth allowing them to be alone with their litter until its weaned. How many of you do it this way? and what size tubs do you use for a lone female with a litter? Any help would be appriciated.