I think I can help you here, ive had hundreds if not a thousand mice bred in my home. I agree with you about rats, mice stink, but rat stink STICKS to you and I cant go in my snake/rodent room for five minutes without coming out smelling like a rat... Anyways. With a twenty gallon tank, get 7 females and 2 males. Depending on where you buy your mice, most are under breeding age and will take a few more weeks after you get them to start breeding, so make sure you give them Plently of time. When I first started it was two months before I had a steady colony going.

Anyways, with those two males, if they start fighting keep the winning one. If not, try to see which one is more interested in the ladys. If you still cant catch them in the act( Maybe I just have to much free time to figure this stuff out...), keep the one with bigger balls. Its all about the male. Period. If you have a mighty mouse stud you will not have to worry about the females not getting prego.

Sounds like you only need 15 mice a week, if you get over crouded with mice do what I do and freeze all the extras just in case they take a breeding break or you do not have enough for the week.

Make sure you have a tank for the weaned mice too once the mom has a new litter ( That is when I remove the pervious litter)

Hope this helps! - Matt