i had the same problem about one month ago...i researched it and found several common 'answers'...phosphates should be checked, lights should be checked, and one person also said that, and im not too sure about this one, to cut back on calcium dosing...i tried everything, and my cyano is gone....i also didnt actaully change my bulbs, but i cut back my lights to be on for about 7.5 hours a day....i also did a partial water change, using freshly mixed water, not the premixed water from the lfs...that water (water strait from the ocean) contains phosphates....also tried changing some of the water flow from the powerheads....now it's all gone....good luck!