Bah this is all wives tales.
Flow
Cyano does not spontaneously form in areas of low flow. If you add a powerhead to an area with cyano you will just move the cyano. It will find a new spot in your tank with low flow and grow there.
Lights
Lighting also has little to do with cyano. Cyano can live and grow under most lighting conditions, it's not that your bulbs are turning a little more red and thus the cyano is outcompeting your corals.
Nutrients
This is the cause of ALL algae outbreaks. Cyano, hair, etc etc etc are caused by an abundance of nutrients. Cyano exists in the air you breath so you will NEVER have a tank without cyano. It's impossible. You can however have a reef environment under which cyano cannot live, that is easy. If you can get your PO4 levels down low and I mean low cyano will have no food. If cyano has no food it can't live.
PO4 will come into your tank via tap water, overfeeding, waste from fish, cleanup crew, corals etc. Frozen food, most "Kent" brand products. Using RO/DI water is a must and using GFOs is also good practice but not totally necessary. If you're good with water changes and feeding/stocking you can get away with not using GFOs. Using GFOs of course gives you some leeway in terms of feeding,stocking and so on.
It's worth mentioning though that PO4 is abosrbed by rocks sand etc so if you have a PO4 problem it will likely takes months (6 or so) for you to get those levels down.