I keep both vampire crabs and red devil crabs in basically the same type of set ups. I keep them in the 70's F. high humidity from 70%-90%, 30% water to aproximately70% land.
They graze through the Java moss all day long and tend to enjoy catching their food. I feed them dusted / supplimented fruit flies, tiny crickets, frozen blood worms, fish flake food I add a tabelspoon of aquarium salt (non iodized) to about a gallon of water. I also keep small pieces of driftwood and live plants in the water to give themselves somethin to cling on to. Molting is when they are most vulnerable. Females tend to bury themselves in wet moss when its time for the young to hatch