I had cyano growing all over my 12 gal tank..it took months to get rid of it. I was using the correct antibiotics for it. I was so sick and tired of fighting it that I tore the whole tank down and started over, I only had a few fish in the tank. I transferred them to the pond/barrel and did the change to the tank. After about one week the cyano died off and now this tank is doing great. I did add new plants and replaced the lighting to LEDs. I'm not sure which change made the cyano go away.