Worms with tentacles in sand bed

[|sCRIBe|]

My send bed has a ton of these things. I see red stringy stuff on the surface of the sand and when I siphon I can suck some but they have a good grip. What exactly are there I am just amazed how many are living in my sand

 

[Fishyfish22]

Spaghetti worm. Good filter feeder

 

[JGT]

Medusa/spaghetti worm. More of a detritus feeder than filter feeder but a good guy nonetheless.