Help me identify these TENTACLES! Good/Bad? (Large Pictures)

[Fredvs79]

I am seeing these all over my sand bed lately, I think they are reproducing. They are orangne/striped hair-like tentacles. At first I thought it was algae, but they definitely curl around things trying to grab them. Around each clump of tentacles the crushed arogonite has a slightly larger size, like they are being pushed up from below. My clown fish hate them, swishing away the sand down 2" just to keep them away from their brain coral. I tried to grab a clump of tentacles, but they retracted, I think a worm may have been at the bottom. Should I be worried? What are they? How do I get rid of them? My starfish isn't eating them I guess.

 

[LeslieH]

Consider yourself fortunate. Those are the feeding tentacles & gill filaments of hair worms, polychaetes in the family Cirratulidae. Lots of people buy them from LFS to serve as CUC and you got them for free.

They are all detritivores. The filaments find food particles which they carry back to the mouth while the soft defenseless body stays safe under the sand. These appendages are distasteful to fish & other predators. It's quite funny to see a fish spitting over & over to get rid of the taste after accidentally getting a mouthful!

There's another polychaete family called Terebellidae, commonly known as spagetti worms. They also have these long prehensile feeding tentacles that pick up detritus. Most reefers can't tell the difference. The appendages of cirratulids - hair worms - that end up in tanks almost always are orange/red/deep yellow with black spots. Terebellid tentacles are paler and almost never have black spots.