20g would be my minimum. A 10g is just too small. The fact that tanks are horrible for housing rodents in the first place (I'm guilty of using them, but I'm gradually switching to tubs), makes using smaller tanks a bad idea. A ten gallon just would not give you the kind of ventilation you'd need for ten mice. I keep no more than five adult mice in a ten gallon. That is even pushing it for me. I keep four adults per 10g on a normal day.

What kind of experiment are you running?