In my 1.5 gals Neocaridinia Davidi Shrimp tank, the air pump got unplugged overnight and I came back to plug it in when I noticed these all over the sides of the tank and nearby plants.
I believe they may be detritus worms, the only thing holding me back is the circular shape of their head. (the lights were out and the sponge filter not running all night)
the second photo has a zoomed-in image of their shape, note the bottom larger one, the lowest part was the head.
I have had a type of detritus worm before and these don't quite look like them. But they don't look quite like planaria either.
The worms did not seem to be on the shrimp.
I want a second opinion before I do anything too drastic.