I remember reading that Sun corals have strong nematocysts in Eric Boreman's book. Also, the fact that the polyps are quite sticky and that this coral is non-photosynthetic and has large polyps and likes to eat meat might indicate that there are lots of nemotocysts.
http://www.fishprofiles.com/interact...d.asp?id=26209
"Aggressiveness: Medium – High. Although slower growing than a lot of other corals, Tubastrea polyps contain powerful nematocyst cells that are capable of stinging other corals that are within their reach."