New addition - Feather duster worm?

[Garibinni]

I just returned from a three week vacation. I had a neighbor top off the tank while I was gone, but no other maintenance. My tank was a little dirty when I got back, but nothing awful. However, I noticed a new addition growing from some live rock that has some GSPs on it.

 

 

The new addition is the white rod type thing in the center of the picture. It has some fans/tentacles coming out the top that retract sometime. I this a feather duster worm, or something worse? Anything to be worried about?

 

The reason I'm concerned is that I've noticed the GSPs around it thinned out considerably in the past three weeks (the pic was taken after the GSPs had retracted for the night). I don't know if that's because of the new addition or because of decreased water quality, but they've generally been quite hardy. I've had the tank since June, and the GSPs since August.

 

I'm about to do a large water change and other maintenance. Should I remove this critter or keep it?

[dadummy]

feather duster, keep it

[BRN]

definitely keep it, you could even relocate it if its not attached to the rock.

[Garibinni]

Thanks for the help dadummy & BRN! Looks like I'll keep it, just wanted to verify it wasn't dangerous.

 

After a closer look, I think the GSPs are thinning out because of excessive hair algae growth. I just did a large water change. If they don't perk up in a few days I'll take a toothbrush to them and see if I can remove some of the algae manually.