MeTree just keep your breeding mice away from any and all other rodents and specifically rats. Rats gives off hormones that will prevent your mice from breeding. I have also heard from several sources that should the mice not breed you have to increase their intake of sunflower seed. That's about all the advice I can give you - my son has three Gerbils families and they are almost the same as mice - just cuter and not as smelly as they do not drip urine 24/7! Gerbils are actually desert animals thus they don't need to loose their moisture, they tend to keep it! LOL
My son has them as pets and feeds some of their pinkies (very seldom) to his snakes!