Found this in my tank yester day it must have been in the rock which i bought in august 2005???? - red with a white stripe running down center. Head looks white for about 1/2 inch, looks like 2 tiny black eyes on it. Posted a few pics, have more if anyone wants to see.
Looks a lot like a bristleworm of the harmless sort, ie, a Pacific: when they're out of water, the bristles tend to collapse a bit, but the one where it's in water looks like bristles. They're detritus feeders.
That's an epitoke of a polychaete in the family nereididae. Epitokes are worms that have become modified in order to spawn. In this animal the anterior paler region is normal but the reddish middle & posterior has enlarged and the parapodia ("legs") and bristles have become larger & fan like so the animal can swim into the water to release its eggs or sperm.
The LFS guy thought it was a bristle worm, but from the pictures of some ive seen they seem to have bigger bristles. I gotta say though I dont like the idea of this worm trying to swarm my tank with his buddies so I think he'll have to go.
There are thousands of different types of polychaetes and they come in all sorts of sizes & shapes. Bristle worm is the common name for just one small group of polychaete worms known as amphinomids. The one in your images is probably a nereid. There would have to be both males & females in order to have babies.
And yup, that's me mentioned on the Cal Academy page. I help them out with worm questions.