That Hydnophora is indestructible. That frag from Sam has been flatworm exited, dropped, buried and otherwise abused and it keeps coming back. We've got it under 400 watters now and it's growing fast - perhaps it will soon be big enough not to keep getting "lost" in the shuffle.
I don't know what those things are in your tank - but they are neat looking.
What a coinsidense! I just found one of these last night while looking at my tank with the flashlight (trying to catch the nightime critters in action). I thought is was some kind of anemone. Mine is red/pink with white/transparent tentacles. Pretty. Hope it doesn't eat any of my critters though.