What is this thing?? [ID]

[k_dog345]

Hey guys! About a month ago I noticed this weird tentacle thing that appeared to be eating the carcass of a dead hermit crab. I saw that it hangs out in the sand bed in the back of my bio cube. More recently I've noticed many more popping up in my live rock. You can see just the black and yellow tentacles. Today I pulled my rocks to pop of vermatid snails that were taking over and I decided to yank one of the strange creatures out of the sand. Here is a picture of it:

You can see the black and yellow tentacles, to my surprise there was a worm like body that came out with the tentacles.

Along with the id, can you tell me if its a friend or foe of my tank? If many more pop up they may become a bit of an eye sore

 

[sc8kv123]

Looks like a spaghetti worm to me. I have quite a few in my tank, I do believe they are beneficial.

 

[saltyfilmfolks]

best sand cleaner ever. also commonly called medusa.
but incorrectly so.
http://www.lionfishlair.com/hitchhiker.shtml

 

[k_dog345]

Thanks guys! Spaghetti worm describes these perfectly. I'll let them be so they can clean up my deitrum. Always learning something new and discover new species in my little nano ;)