I keep Red Devil's that I've been breeding for 2 years. They're pretty easy to keep, as long as they're well fed. From my experience, the crabs really demand substrate they can tunnel in and pick through for food. They don't need much water, just a constant source. They young crabs seem to use water for protection more than the older ones. They're hunters. Fruit flies and other live foods are really their preference. They'll take a variety of foods but are much more vigorous and enthusiastic when hunting live prey.
here's a video of them in the wild. http://youtu.be/y5KeoT2VfzQ