White stringy worm ID.

[mkroher]

I see about 6 or so in my tank. At first they were just on the glass. Recently one attached itself to the base of a frag.
When I first saw them I thought it was sand stuck to the tank (in the shape of a worm), I used my magnet to wipe it off, and it was very stringy and long. If I were to stretch it end to end, it might be a few feet long. It looks like sand bunched together, but it's actually a thin string type bunched closely together.
Can anyone ID this? Thanks.

 

[btldreef]

My guess would be Polychaete - Chaetopterid

 

[bang guy]

There are quite a few Bristleworms that build structures like that. If you are really unlucky it might be a Eunicid but the odds are in your favor that it's a beneficial worm.

 

[mkroher]

Thanks for the replies. But it doesn't have any bristles on it. No legs. No (visible) tentacles. It's just... a white string bunched up.

 

[spanko]

Do you have a sponge in the tank. Resembles Polydorella prolifera.

 

[katsafados]

Could it not be snail eggs? Does it move by itself? I know my snails were laying a ton of eggs at one point and it looked like stringy stuff bunched up on the glass.