Causes Of Cyano
It seems that a nutrient rich water problem is the prime culprit. Not that the Cyano is eating left over food particles, but left over food particles are breaking down into harmful excess nutrients. Add Light plus dissolved organic carbon/organic material ( D.O.C ), and you have a great recipe for the preferred Eco-System of CyanoBacteria.
NOTE:
It is good to know that Poor Water Husbandry is usually the culprit in most "problems" that develop in the Marine and Tropical Eco-System.
It is said that the Red Nightmare is caused from Phosphates and Silicates in the water column. But it is not that simple. We have seen cases develop from Old Bulbs or a Lack Of Good Water Flow .. but we have never seen that the addition of a correction of these two "causes" ever made the Cyano go away.
In fact, we had two cases of outbreak where the systems were absent of Phosphates and Silicates, they also had new Halides, Actinic's and Great Water Flow. What was surely something to think about was the fact that we had switched to a new Flake Food. Another factor is that we have never had an outbreak unless the system housed FISH ... and they were being FED!