The moisture gradient

Most terrestrial isopods breathe with gill-like structures. They need moisture, and they also need a place to escape if the wet side is too wet.

Set the bin up with a moss or soil pocket that stays damp, and a bark or leaf side that can dry. If every surface glistens, you have gone too far. If the moss crumbles, it is too dry.

Write down what you see. A note such as "moss damp, dry side crusty" is more useful later than "watered the bin."