When having corals I really don't want to upset by chemicals, I like to really focus on getting stable levels of nitrate and phosphate(above 2 ppm NO3 and above 0,04 PO4). Then make sure as many other parameters, like temp, light schedules, feedings etc, as possible are stable and not changing. It might take 2-5 weeks, but usually the Cyanobacteria will go away by themselves. This is what we have done for 7+ years now at my work (public aquarium, many reef tanks

).
This is for when the nutrients are low. Cyanobacteria when having high nutrients might be a bit trickier to get rid of IMO. But stability is the key I think. Cyanobacteria is opportunists and do well in unstable environments.