They look like sm feather dusters...

[peteyboyny]

Been watching these grow on a rock for a while now. They're only on one rock. Not sure if they're harmless dusters, or some type of hydroid? They rock they are on also has some yellow and purple sponge growing on it. Just want to know if I should get this rock out or not, and whether or not I will get stung. Thanks.
http://m1268.photobucket.com/albumv...VNb6G05t/9Uc2bXPFl/8e6WfCTGlDLD7D9R2Vd4KUrlM=

 

[thirty5]

They Look like feather dusters to me. They are fine IMO

 

[JonnyJ]

dusters, aka good stuff. Sometimes they will multiply out of control to combat over feeding.

 

[peteyboyny]

Cool. That's what I was hoping. Thanks.