I like them!
You can try to have them on the rocks, if you really want to.
They normally look better on the sand though.
If they were really collected originally from the sand (we never know if that is another "cartoon name" so they can $ell them for more money!!!) they will do much better on the sand.
Use fine oolitic sand, not gravel. Sugar size aragonite is the best. You need to have them on a little individual pebble for each polyp (use super glue), than you dip the pebble in the sand. That will help them to stay there, not to wonder around the system.
They are normally greenish/brownish and the ones I've seen in the wild look very much like Protopalythoa spp. (tapering tentacles, solitary polyps), but they could be another species. The ones I'm talking about are not Zoanthus spp. nor Palythoa spp. for sure!
Feed them once a week in order to keep their color and size. You could offer Tropic Marin LPS pellets or something similar. They like Life Spectrum for marine fishes too. One to two pellets per polyp will do it.
Moderate current and med to high light. I would say 79 - 81F for the temp.
They love metal halides!!! T5s are good too!!
Make sure you adapt them properly to your light and that your system is mature enough, not dirty!!! :thumbsup:
Good luck!
Do you have pictures?
Grandis.