What should I put into my hermit crab iso tank?

ok so I have 2 Hermie's Zig and Honey Bee. Zig doesn't do much. He digs alot and sits in his hermie hut and never comes out. He is alive cause I play with him and Honey Bee every day. He has started to turn red and I bath him in lukewarm water. Is he fixing to molt? Also I have an Iso Tank ready. What should i have in the Iso. tank?