I think they are expert only, mainly because of their special diet. I believe they only eat a special algea called...briopsis? Anyway, people usually buy them to control algea, not knowing that they are slowly starving because there is no briopsis. Other's buy them to control briopsis if they know they do that.
Other than that I think there are no problems, except for them being sucked into power head pumps.
If I am describing the wrong critter please correct me, as i am not 100% sure.