In my opinion it's never good to leave the males and females together all the time for any rodent. It's best to pull the females just before giving birth and put them in separate tubs. Once the babies are weaned you can put them back with the colony. Otherwise they will get pregnant as soon as they give birth and will have the second litter before the first are weaned. And if you try to wean the first litter early by separating them it seriously affects their health and their growth will be stunted. If you keep them all together there's a chance the new babies won't get enough milk to survive. I separate both my female mice and rats before they give birth, or at least remove the male as soon as one is ready to give birth.
If you are not in a hurry you can keep the male in the tub until all are pregnant, then just before the first female gives birth feed off the male. Then as the babies grow up feed off all but one male first, keep that male to breed back with the females. I sometimes do that with my mice, it really slows down production but keeps the females healthy and litter sizes big. Plus with mice it's the males that really stink so it helps keep the smell to almost zero by removing the adult male population. I don't really need that many mice since I have so many rats so I'm not in a hurry to produce that many anyways.
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