everyone does things different, for the time being i have a large communal aquarium that i breed my rats in. it houses 2 males and 9 females just fine. when i notice that one female is preggers i pull her out and put her in a rodent lab cage and she stays there till her babbies get fed off or until the babbies are weaned. my asfs i just keep in the lab cages for all of their life.