Is this a problematic spionid?

[DaJusticeKing]

I’ve found a small number of these on the glass over the last couple months. They’re pretty rare in my tank. My guess is some kind of spionid, but I’m not sure if it is a problem yet.

I know some of my hermit crabs have come in with (possibly boring?) spionids in their shells, but these were larger, flatter, and redder than this species I am looking at. So is this also a problematic boring one, or is it one of the beneficial ones?

 

[Gumbies R Us]

@ISpeakForTheSeas

 

[ISpeakForTheSeas]

@ISpeakForTheSeas

Hmm, hard to say for sure from the video (I would need closer pics of the head and the "feet" - notopodia - particularly showing if there are any differences in the notopodia between the lengths of the body where the color of the worm changes).

That said, these worms are most likely harmless, and Spionid is a solid guess from what I can see of the worm.