Hi Jason - I think that they are reasonably hardy. I have seen some in Wayne's coral bath for weeks on end - surviving without problems.
They do not require or like TOO much water flow. They are filter-feeders, so will "eat" from the water column. You CAN feed marine snow or phytoplankton (ie coral food), IF you want....
If they stress, they can loose their "heads" (the "feather part"). I am quite sure SOME types of angels will nip at them. Perhaps some butterfly's as well.
Not sure about the other fish we keep.