I am dealing with cyano on my sand bed and on some rocks. I have tried siphoning the cyano out of the tank. Only for it to come back again. I cant seem to understand what the cause of the cyano is. My paramaters are great, coral and fish all look very healthy. I am running at ULN paramaters now. I am thinking of doing three days of lights out. I understand this can be a temporary fix. I don't know what else to do. I changed the rowa phos media. Any advice is much appreciated.