Hitchhiker with loooong legs

I just put into my tank its first inhabitants: a peppermint shrimp, clown, Xenia, and 4 small crabs. 5 hours later noticed this tiny little shrimp looking thing with very long tentacles. Can anyone ID this this and tell me if its harmful or not?

Picture:

 

Spaghetti worm, good part of your fauna, safe

 

Thanks, 2in10. I was worried it would hide in the tank and be hard to remove if bad, so I was hoping for a quick response!

 

It most likely will move to the sand or your rocks.

 

OK, cool. Right now its hiding behind my cleaning mag.

 

It might stay there if it gets enough food. Shouldn't once you use the mag though.

 

[QUOTE=PlanB;1096994 i have lots of spaghetti worms or at least had