So, you have 25 tubs in all, correct? If you had a group on three females in each of the large tubs(At least 6.) And you rotated the male around, into one group of females each week(For a week.) then you could have three litters born every week from just that one rack, and with only one male. The average size per litter is 10-15 so let's say each rat has 12 babies. That's an average of 36 babies per week, or 144 per month. All the extra tubs you have could be used for grow out tubs, to put any babies you haven't fed off yet. You could keep them in the 13 mouse breeder tubs.

When a female starts to slow down in production(Usually around a year old.) You can switch her with one of the grow out females, same with the male, though they usually still produce with age.

So, every week, you'd just put your male into the next tub. This would also give each female a two-week break after weaning her litter before being bred again. You can also just put one male in each tub with the girls, but this means instead of having those litters split up into a few every week, you'd have all 18 at once, so you'd have an average of 216 babies a month, but all at the same time, and the females won't have a break between, which can tire them out quicker. Plus, you'd have to have five more males, lol.