Cyanobacteria is not an algae so unfortunately your the AlgaeFix won't help, it will probably help with other types of algaes though. Cyanobacteria is a bacteria, and I agree with ghost, and have seen many have growth spurts of Cyano, while using a carbon source. So I would avoid that.
Cyano in most cases is a result of high nutrients. How much of what kind of food are you feeding? How often are your water changes, and how big are they? How much flow do you have in the tank now?
A few good things that I have seen to help eliviate Cyanobacteria is;
More frequent larger water changes, 20-25% weekly.
Increased flow, add a couple of power heads Modded Maxi-Jets work great and are very inexpensive.
Decrease feedings, or types of food. Never underestimate the amount of phospahtes that are in most standard flake foods. Try cutting back to once everyother day, depending on what types of fish you have.
How big is the tank? How old is it? Inhabitants? Do you have a refugium? Are you running filter socks? Do you run Granular Activated Carbom(GFO) or Granular Ferrick Oxide(GFO)?
Good luck, and I hope this helps.
Spleify