wierd pink worm-like things

[sasquach]

Ok, this is my moms tank. We've had this tank setup for a couple years, and have noticed a growing population of these pink little worm things in the sand. They are more of a cetipede like body structure, and they are everywhere. We never have any problems with the health of the fish (except for the occasional suicide escapee), but recently noticed a fish with some wounds on the tail end. These wounds look like gashes, as if something has taken bites out of his tail. The fish is an eel like fish (not sure what it is, cause i didn't buy it), that lives in burrows of the sand that he creates. I've looked around for info on flatworms, but can't get a description that resembles my new inhabitants. We have to dragonettes, a manderin spotted goby and one other, and we just bought a purple nudibranch(possilbe predators of these worms). Anyone have feedback as to what these things are and if they are harmful?

 

[beth]

Look like This

 

[sasquach]

well, sort of; didn't see anything exact. What i have looks like the bristle worm/fire worm mentioned in the first picture, but much much smaller. These things are about... say... 1cm in length, and they only seem to inhibit the sand(live sand). They aren't even on the surface of the sand. The only way you see them is where the sand comes above the trim of the tank, and you can see tons of em burrowed underneath. We do have quite a bit of sand in the tank, live rock, and a few coral. We have a number of hermet crabs(only the bigger ones survived our snowflake eel) and a fireshrimp as bottom feeders. We're gonna try to take a sample to the local shop. But thanks for the input so far, any other information is welcome. =)