I have been reefng for about six years and I have never run into a cyno problem. BUT once I started using bio pellets back in August soon after the cyno came. I used Chemi-clean for he first time in October after being very hesitant about putting something in my tank with the name "chemo-clean " sounds like a floor cleaner. It works ! and it work great just make sure to take you skimmer cup off or you will have a big mess
