I have a friend with hermit crabs, so I’ve heard her talk about they need a moist environment...but that is the limit of my knowledge. This seems different than the mounding moss from the other post, but don’t really know enough about the living mosses for terrariums to speak with any confidence. When I’ve used moss, I always went with the tried and true sphagnum moss...easy to get around here.
A sponge would be a good idea, particularly if you’re just going for a humid hide. Right now I have a little container with wet towels in Belle’s cage because the drop in humidity from the heat has given her a stuck shed. I’ll soak if I need to, but I’m trying to let her do it on her own first. She’s fussy enough about feeding without me adding any additional stress. On the plus side, she’s eaten 3 f/t hoppers in a row. Yay, no more live fuzzies!