Feather Duster?

[brittant]

I bought some coral frags today, and noticed a small green tube on the base of one of the rocks. Sure enough, it opened up with white, lacy fingers that look like a flower. (I'll upload a picture when my camera batteries charge enough.) Is there anything that this might be other than a duster? If it is a duster or tube worm, could it be harmful to anything in my tank? If it is harmless, are there any readings or guides on the care of dusters that you would recommend?

It looks a fair amount like this:
http://www.maui-scuba.com/wrecks/arizona/images/feather_duster.jpg

 

[little_fish]

They are filter feeders and dont need any special care, but please dont double post.