Mouse tub furnishings?

[ctrlfreq]

What should I put in the tubs with them to ensure that they feel comfortable and safe?

We tend to put a couple small hides (just like with the snakes), some torn up paper, and a mouse wheel in each tub. The safe part, I've found, is more about leaving them alone than anything in particular you can provide them with.

I'm constantly having to chase one or more of them off of the tops of the tubs. Do you think that'll ultimately foil my breeding plans, or do you think since the cats can't actually get to the mice they'll be ok?

We have ferocious hunters ourselves, and they will snap up mice whenever they get a chance. The biggest thing to remember is that cats are cats, and they will be curious. If you have them where cats can get to the tubs of mice, then make sure they are secure, and not able to be knocked over etc. It won't take long for the mice to get used to the cats and not see them as a threat, as long as the cats can't get to them (ie. knocking over the bins etc).