I think what I'm planning on doing is having three females each in their own ten gallon. Then I will rotate a male between them. I hope to get the system down where eventually the timing will be just right so enough rats will be ready when I need them (with some left over probably). If I get to many I'll just stop putting the male in with the females for a while.
Question though...do you have a lid for that tub? Or do they not try to climb out?