I was carefully watching it extend extremely fine filaments from the underside of the coral. I had noticed these before and thought is was just another small worm living in the tank. However, after studying these long enough I realized that these were tentacles and the coral was feeding. You see, the coral would let these out and would let them drift about. The coral would then rapidly reel them in. Look closely at the first photo below because the tentacle is difficult to see because it is so fine. Each tentacle has one main strand with small "rungs" hanging off of it.
These tentacles appeared to be able to extend 4 or 5 inches beyond the edge of the coral. My green open brain was in stinging range of these tentacles so it got moved a few inches further away.
Here are a few more pictures of my rose brain coral.
