Fighting after cleaning?

[Sita]

Is everyone else missing the part where OP said they've been living together fine for 6 MONTHS, yet they only tussle for a couple minutes when bedding is changed?

Granted it IS a bad thing that when they fight, SOMETIMES they draw blood (again, didn't say every time), but if using the old bedding trick works, there's no reason to kill one of them.

I sometimes have a full cage of several male mice that I'm growing out as larger feeders, and I rarely have problems with any fighting, even if I add new males from different cages. My method is that when I need to add ones, I clean the tank thoroughly to get rid of any old scent, then before I put the old and new mice in there, I take a small handful of the old mice bedding AND the new mice bedding (dirty) and sprinkle it throughout the cage. Sometimes there's a brief tussle that is resolved quickly, but most of the time they just run about sniffing each other, then settle down.