I think you've got chicken mite (also called red mite, roost mite and poultry mite). This is a very nasty one and hard to get rid off. During the day they hide in dark places and the suck blood during the night.
There called chicken mites, because they are mostly found on chickens and other birds. But the actually feed on all mammals, including humans. They can live up to 6 months without feeding. In warm conditions the can become a real epidemic, since the life cycle may be completed in only 1 week.
First treat all your mice with ivermectine (Beaphar) or selemectin. Then you'll have to treat the hole room/place the mice are in. Just ask the local petshop about a spray agains chicken mites (it usually it has a bird on it). Tread every mm in the hole room, especially the dark spots and cracks. Ventilate!!! You also have to treat your cages with it. Read the instructions well, you'll have to use it more than ones, with some time in between.
You can't see 'normal' mites. They're to small to see with the naked eye. You can only see the effects the have and sometimes the eggs. In this case just using ivermectine twice with a week in between will do the trick.