Dinoflaggets is not the same as diatoms.It seems I really need to get those diatoms on the sand under control.
Unfortunately you have dinoflagellates.
Syphone out what you can, however you can. Top the tank back off with nsw. Shut the lights off. Get a microscope to see what type of dinos you have. And then we can go from there to correct it. Feed minimal, if you can wrap the tank in the blanket to keep light from getting in.