Algae ID - Its starting to grow on my corals

[AL'S AQUARIUMS]

Does anyone know what I should do about this algae? My nitrates test zero with redsea test kit. I don't have a phos test kit but I did put in some gfo in a media bag 5 days ago. Still no improvement. I'm thinking about shorting the light schedule next.

 

[KJ]

Dinoflagellates.
https://www.reef2reef.com/posts/4075259/

 

[AL'S AQUARIUMS]

Dinoflagellates.
https://www.reef2reef.com/posts/4075259/

Thank you! I'll have to do some research on the best way get a handle on this. Appreciate the ID.