Please help ID this

[Caige]

maybe good polyps or Feather dusters?
I hope it's not Colonial Hydroids....

They are brownish and do go in when touched (with feeder stick).

 

[Kurt_Nelson]

Picture is too fuzzy to really tell. They kinda look like colonial hydroids, but seem to be too densely packed. A clearer/closer picture would help...

 

[Caige]

I'll try to get a better pic tonight... .if it is colonial hydroids -- what causes them and is there a way to get rid of? What is so bad about them? (this is where Melousa jumps in with a link) LOL

 

[melosu58]

Xtalreef

You can find something about them here. Right on cue. LOL