cyano bad!

Do you have a TDS meter to measure your RO water that you are putting into your tank?

 

I've got it too. Cause... upgraded lights from pc to 8X54 t5ho. If you really want it dead now make it totally dark for 3 days, then do a water change. That is hard on some corals though. Cyano will probably come right back anyway. Your new lights probably "illuminated" your problem. I am using more frequent water changes, more snails, more skimmer, and patience. I've cut down the photoperiod for white light and cut down on feeding. It is getting better but seems like its going to take a month. On the other hand... are your corals showing growth?... mine sure are.

 

i have also used chemiclean and it worked awesome. Did not kill any corals and that crap was gone. Before you dose make sure to get as much out of the tank as you can, it says that in the direstions.