They are a great coral, but one thing negative. Each polyp must be feed or it will die. This can cause some negative effects on your tank due to excess food in your tank. Just something to think about.
MBL
This is not a great picture, my macro is not that great for long shots. This happened in back of my tank. It lasted approx a half hour with lots of small orange (eggs I think) being released from the starfish.