[b][b]what Is This???[/b][/b]

good morning LIVING REEFS! can you give me more infomation on the sabellid worm? I read JHNRB article and did a yahoo image search for the type of worm I think i have in my tank. It appears to be a sabellid worm but it has no crown, it has a hole in the rock at the bottom, I captured it on my camcorder using the night lite and what i seen is that it extended out of its hole at least 6 inches or more, it appeared to be pulling algae off of the rocks but I am not sure. Is it a good worm to have? It's pretty long, not sure how long when fully extended, it retreats when the lights come on. There's nothing else in the tank other than about 35#'s of live rock and some (CaribSea) aragonite sand.
Thanks
Darieus
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tank spec:
55 gal
35 to 45 #'s lr
caribsea aragonite sand 2 to 3 inches

 

Is it bristley at all if maybe a fire or a bristle worm.Here are some other to search for Eunicidae worm,peanut worm(might be this one I had onemy first tank that would come out at night and strect to the other side of my nano befor e I remve the rocked and spray with hot tap water)here is good web site on worms
http://www.mesa.edu.au/friends/seashores/worms.html