Microscope ID help

[NotApplicable]

So my ~3mo old tank is doing well overall, except for an unsightly brown layer forming on the sand. I took this video and see at least 3 distinct… things in it. Any pros recognize?

I think the smaller circles may be amphidinium Dino, no idea on the others. Could be wrong!

Freeze frame:

 

[Dan_P]

Diatom species and pointer tip at Amphidinium dinoflagellate.