Cyano is a sign that your water quality is not as good as it should be. Have you tested your phosphate and nitrate levels recently?
I had a cyano outbreak in one of my tanks and defeated it with frequent water changes (a few gallons every day), siphoning the cyano from the sandbed (every day), increasing/adjusting my flow to eliminate dead flow spots, and using Phosguard to bring my phosphate levels down to zero (or close to it). Took about 2-3 weeks. At the same time, you must address the root causes that could be causing water quality issues (e.g., too high a bioload, overfeeding, inadequate flow, etc.).
Hope this helps you get started on conquering the problem.