White wormy guys?

[OpusOstreae]

I have a 20 gallon sand-substrate tank, containing 2 5-keyhole urchins, 2 1 inch stargazers, and a whole bunch of brittle stars. Today, I noticed about 50-100 little white wormy guys on the glass of the tank. They're only a millimeter or two long, and it looks as if they have an exoskeleton-they only bend in the middle. I can't get an in-focus picture of them, and my eyes can't focus that small! They all seem concentrated around (though not on, and a good centimeter away from) one of the brittle stars. They don't touch it at all, though they do scoot closer and farther away.

I'm at a loss, and can't come up with a better description! Any ideas what these could be? Are they a problem?

 

[sweeTang21]

called glass worms im thinking. usually can be scrapped off and syphoned out of the tank. I have however also seen amphipods grow in a little cacoon sort of thing and hatch that way. My bet goes toward glass worms though.