Yellow worm-like creature

Question
Just appeared this evening.  Is very slender, about 1/2 inch long, bright golden yellow. Has a few of same color "threads" wrapped around it - with some of the "thread" ends floating loosely in the water.

Answer
Hello Laura. This worm sounds to me like some kind of polychaete worm. Possibly a terebellid or a serpulid. Basically they are related to your feather duster worms with out the tube. They burrow their bodies into the gravel and leave their threadlike tentacles stretched out along the substrate. They feed by catching small particulate matter in these "threads" which they than pass down into their body. Harmless, These worms are not stuck in one spot like your tube worms. Though they generally don't move around much unless disturbed or looking for a better place to feed. It most likely came in on live rock and there is probably more of them!