Need some help with identification

[Tim]

There are various things growing on my live rock one of which I think is quite beautiful when it bobs around a little in the current but I have no idea what it is. It spreads like wildfire though . Anyone have any idea what it is?

The thing in question



And another shot with B a s t a r d the Electric Blue Hermit(He earned that name because the first thing he did when getting into the tank was steal another hermits shell) in it because he happened to be crawling around it looking for scraps

[Corvus]

hydroids

http://www.wetwebmedia.com/hydrozoanfaqs.htm

[Tim]

hydroids

http://www.wetwebmedia.com/hydrozoanfaqs.htm

Thanks for pointing me in the right direction. They seem to be a nightmare of reef tanks, but since I don't have any expensive corals at all. I don't particularly mind them being in my tank. Can't find anything to indicate it being bad for fish. It makes for a nice contrast with these hybroids in the background and the green puffer in the foreground.

[Corvus]

I do have a small colony since many years, carefully watching them. So far nothing bad happend. They may take over some tanks, but apparently not all.

[Tim]

I do have a small colony since many years, carefully watching them. So far nothing bad happend. They may take over some tanks, but apparently not all.

It's doing a good attempt here but I think the macroalgae I have are winning, since I actually have to take away some of it to keep it from completely overrunning my tank.