colonial hydroids?

I set my tank yp three weeks ago and this came on the first live rock i bought i thought it was pretty cool untill i started looking around on this site so i just want to make sure thats what this is and if i need to get rid of it thanks.it does open and close when my crabs get near it.

http://www.3reef.com/photos/showphoto.php?photo=7288

 

Yup, you've got droids I noticed a few in my tank a few in my tank a few weeks ago so I have to figure out how to get rid of them without killing the 3 sps corals that are on the same rock that they're growing on.

 

Just when i think my tanks doing something cool oh well i guess ill wait to find out what to do.

 

So, what did you do to get rid of them?

 

I haven't done anything yet. I was thinking of smearing kalk paste on them but the fact that they're touching 3 sps corals is keeping me from wanting to try something that drastic. I'm still weighing my options at the moment and will update if I find anything that works.

 

Crap so that's what they are. Appears I have them to. Do you think hitting them with some Joe's Juice will kill them??

 

It's worth a shot. Try it and let us know if it works!

 

So, why does one want to get rid of them? I have them on a few of my rocks and one of the rocks has green start smothering them.

 

Some claim that they can sting neighboring corals, some claim that they can grow to plague proportions and smother out corals, etc. etc.

 

So in other words there is not proof that they do these things often, but there is a chance they may. I'll just leave mine alone and see what happens.