These guys tend to produce thier own moisture and humidity. I keep them on no substrate eggcartons and with an open lid high enough they cant get out of course. The open lid is fine since its in a closet where there are no air vents. If you keep them in normal rooms a lid to hold in humidity is ideal. I give them pretty wet food watermelon and cantalope rinds, apples, oranges. The wet food translates to wet frass that holds humidity really well. In fact I frequently replace eggcarton because it so naturally damp. You never want soggy though thats a recipe for flys and anarobic conditions which is really unplesent. Also the isopods might work but they will most likely be eaten. They seem to ignore beetles and thier larvae.