I agree with shutting down the lights for an acceptable period, increasing flow, reducing the hours for the lights (after the initial 2-3 day off cycle), and feeding reduction.
I have a tank at my school and we ALWAYS get the cyano when someone forgets to turn off the light on a weekend or they over feed (they don't listen to me...I have a sign that says DO NOT TOUCH...).
So, at least 3x a month I go through this. It's not heavily coral dominated though, and mostly softies. After the 2-3 day of only ambient light, they shed and are back to normal.