What is these white worms??

[youdontknowme]

There's around 5-8 of it appearing on my front glass after my pair of true perculas sweeps the sand away to make a pit hole. What are these things??
Heres a pic attached.
Moving super slow, and have lots of super small legs.

[vitz]

the pics too fuzzy-but it's some type of eunicid. a quick google image search should help ya out :)