I have been keeping 2 live Cepaea nemoralis. I haven't bothered to look up how to best maintain them in captivity; I just put them in a plastic box with some wet paper towels and carrot skins and pieces of lettuce for food. There are several piles of fecal strings in the container, indicating that they are eating stuff, including the paper towel.
However, I often see them stuck on the underside of the lid as if they have a requirement to become dormant frequently. Last week I kept them in a dry container for a couple of days. When I examined them again yeaterday, the smaller one had sealed its aperture with an epiphragm.
You can see the pneumostome (breathing hole) of the of the snail on the right.
I returned them to their regular container and sprayed them with water. Earlier today the smaller snail had come out of its shell. Tonight they are both stuck on the underside of the lid again.