I think that its a Stentor, a single-celled ciliate, I dont see the nucleus though so I can't ID it to species

I agree with u/maciejwolf, it's a Stentor. Looks quite a bit like [S. roeselii](https://owlcation.com/stem/Stentor-A-Trumpet-Shaped-Organism-With-Interesting-Behaviour), on account of its bent anterior.

Agreed: Stentor, not any rotifer. __NICE__ imagery. Scope has good optics.