Ok, so a good set up would be three male tubs with 3 females per male. Keep the females with the male unless they are pregnant, then move them to a maternity tub where she will give birth and raise babies. After 3 weeks of gestation, and 3 weeks of raising and weaning, move her back in with the male?

So as far as number of tubs we are thinking 3 harem tubs, one for each male, say 2-3 maternity tubs, 1 vacation tub, and 2 feeder tubs.