[Cait]

I personally don't like barred cages. They allow drafts to get to the mice and of course they kick bedding and food out everywhere :roll: But I would think 6mm bar spacing should do the trick (easier said than found I believe). If you can get your little finger through it, the mouse can get through it easily. It would be safer to get a plastic or glass tank, but it's up to you, some people do use bars.