I have to disagree with the above, IME star polyps can and will sting, depends on the particular coral though, I have them in both of my tanks, in one that star polyps sting certain acros they come in contact with, in another they are stinging a colony of Zooanthus sp. They can also grow quite fast under the right conditions and take over rocks and other corals. If possible I would suggest isolating them to a single rock that does not come in contact with other rocks. HTH