A little history lesson first. I had a mild case of a cyano
presence in my tank, tried the cures that I read on here; vacuum & less food, with limited success. I was going on a 2 week vacation so I asked my neighbour to watch my water level and left him 2 servings of tank food. I shut off the MH
lights and skimmer but left the actinics on the 12 hr timer. Low and behold on my return there was no more cyano
I hope that does it I will give it a few days and see what transpires.