I read that cyanobacteria doesn't like water movement and oxygen. I
also read in some places that it appears when nitrates are very low.

I will do a partial water change... and get more water movement and
aeration. I was minimizing aeration to keep the CO2 in the tank but it
might be better to increase CO2 injection and aerate at the same time.
I will also add more nitrate in addition to the regular amounts.

Will let you know what happens.