That’s really looking like Dino’s- how old is the tank and what are the parameters? Do you see bubbles on the brown mat?

From what I’ve learned and from my experience with dinoflagellates it occurs when you have an imbalance/ very low nitrates or phosphates. (I got Dino’s a month into the tank from low phos and nitrate because I was keeping the tank too clean). you won’t really know if it’s Dino’s until it grows over everything, is wispy and has bubbles, or you id with a microscope, if you have a uv sterilizer I’d run it and do a water change in hopes of nipping it in the bud.

Maybe more flow

My opinion as well copepods