We have a few small feather dusters in there, a snake polyp and a chili coral too. All none agressive and low light requirements. We've had them for about 6 - 8 months now.

They come out off and on throughout the day, but they know when feeding time is and will come out and stare in my direction. They used to dart back into their holes when anyone came close to the tank, but they now make an exception for me. lol

they get along just fine with one another, just a bumped head now and then going after the same piece of food. We had seahorses in the tank with them (Kelloggi, yes our lesson)and they now have a green filefish neighbor. Just have to have peaceful cohabs in with them.