Small critters moving around on glass

[mr11]

The conclusion I jump to based on the title alone is amphipod/copepod/something-pod but as far as I can tell there aren't legs or antennae or anything like that. They are super tiny so maybe I just can't see enough detail. Also they seem to move more like a slug/snail and glide around on the glass. The best video I can get is below. Any ideas?

 

[Pfisherman]

Flatworms.

 

[mr11]

Yep nailed it. Thanks. They seem to be Amphiscolops or at least not the red planaria flatworms. Will a Melanurus eat these?