They're fairly easy, though are not 100 percent reef safe, as they'll usually eat any shrimp you have. They won't bother any corals, clams or anemones at all though. A friend of mine, who has a beautiful one, also set up a simple planted FW tank, to breed Mollies. His Frogfish will jump into the net, to gobble up the Mollies.
Once, I was attempting to photograph it, eating. I had my camera set to burst mode, where it takes 8 pictures per second! In one photo, the molly is sitting in front of the frogfish, in the next photo, the molly was GONE! It's so quick it's amazing!