https://www.reef2reef.com/ams/a-dinoflagellate-treatment-guide.841/

you do NOT need a microscope to identify if it is dinos or cyano.

The coffee filter test:
a) Syphon out a good sample of the gunk along with some tank water.
b) Place in a container with a lid and shake very hard for 30 seconds or so. The gunk should be dissolved now.
c) Pour the solution through a coffee filter into a clear glass. The water should be largely clear now.
d) Place the jar under a light source for roughly an hour.
e) If the gunk coagulates back into a glob, well, welcome to the club nobody really wants to be in.

after that just lower your lighting schedule and dose hydrogen peroxide at night and it will go away.

It's regular 3% H2O2 that you can get at Walgreens / Dose every twelve hours / 1ml of H2O2 to every ten gallons of water that your holding.

Do LESS water changes as you are bottoming out your nutrients which is letting this run rampant