I have the type in the picture above also. I have found it to match photos of hydroids know as myrionema. I have tried all sorts of things that I have read about in books. Butterfly fish, keyhole limpets, manual removal... Nothing seems to work. If you let any of the colony float away it pops up somewhere else. I have too much of it to try to cover it up or remove the rocks to be treated. I have read that the nucibranch Pteraeolidia ianthina also known as blue dragon will eat them, but where do I get one. Any help would be greatly appreciated. PLEASE HELP!