TBS Live Sand - 1 in. worm/something

[fishpicklepaste]

Hi all, can somebody ID this hitchhiker for me? It’s about an inch long and is extremely squiggly when its running around.

 

[JoJosReef]

Actually not a worm. Called a lancelet. Filter feeding chordate. They die off and are harmless, although a bit freaky with how they move when disturbed.