Help w/ algae or pest ID

[jptrson]

Can anyone ID this, at a glance it looked like an algae, but retracts when touched. In the picture the rock is about golf ball size. It's in a friends tank and he has taken the rock out and scrubbed it, but has come back after a few months. Almost looks like little brown Dandilions?
Thanks

http://reefcentral.com/gallery/showphoto.php?photo=240747<a href="http://s78.photobucket.com/albums/j88/jptrson/?action=view&current=a1366.jpg" target="_blank"><img src="http://i78.photobucket.com/albums/j88/jptrson/a1366.jpg" border="0" alt="pest"></a>

[saltycreefer]

Look like hydroids which really suck. Throw it out.

[jptrson]

Thats sorta what I thought, but I've never seen any. Like an alien life form to me, but might give me a place to start doing some research. He says his tank is loaded, but I'me not sure how big his tank is or how much rock.
Thanks.