[trilinearmipmap]

You could look at cyano as a symptom of the problem rather than as the problem itself. And if the cyano lives on nutrients (waste) such as ammonia/nitrites/nitrates etc, killing off the cyano could release these wastes into your tank. I have some cyano in my tank, typically in low flow areas. The only time it ever harmed a coral was when a pocillipora was not given enough flow, and the centre of the pocillipora got covered by cyano which choked it off. Anyway my view is that the cyano is an aesthetic issue and killing it off may cause more harm than good.