I have several of these in my tank. They're orange ball anemones (isn't actually an anemone, but a corallimorph). They appear to be non-photosynthetic carnivores, as you've found out it already. I believe Melev has them listed on his ID page as reef safe, but the balls on the end of their tentacles are mighty sticky and probably sting it's prey. I would be careful where these are placed in proximity to corals, but most likely they will retreat to a shaded area where there are no corals.
Here's one in my tank that caught a Collonista snail. It's roughtly the size of a nickle.
