Please ID this for me

[ReefObsessor805]

Hi everyone,

This has been in the front corner of my tank for some time now. I wasn't sure if I should have pulled it out or not, so I'm consulting you experts before I bother it. (Sorry, glass is a little dirty right now.) What is it? :idea:

Thank you for your help!

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[LeslieH]

Those are the branchial filaments of a cirratulid polychaete worm. These worms, often called hair worms, are deposit feeders and quite beneficial. Many LFS sell them as part of clean up crew packages. Here's a pic of an entire worm -
http://www.flickr.com/photos/80125969@N00/396799260