Cyano is that slimey (usually maroon colored) film that grows over substrate. I find cyano blooms under three conditions:
1) high nutrients, solved by regular water changes, protein skimming, activated carbon, controlled feeding, good top-off water, etc.
2) shifting light spectrums, which can sometimes be fixed with changing old bulbs.
3) low pH, ca, or alkalinity. Raising both has helped curb cyanos in my tank.