I had really good luck with a chocolate chip star in a sem-reef setup. It was my first tank, and I didn't really know what I was doing, so I guess that just proves how hardy those stars are. I've heard terrible things about them capturing fish and destroying reefs, but my tank was only 10 gallons and he never bothered any of the fish or anemones and zooanthids I had in there. Of course, I don't think I'd trust one with acroporas or other stony corals, but I think a chocolate chip would make a very interesting addition to a fish only or soft/LPS reef tank. Mine was always active and a real pleasure to watch.