Alas my new tank (2 years approx now I think) is suffering the same problems my old one did and it seems no matter what I do I am always fighting with cyano.
My lights are LED (AI Vega).
Flow is via 2 MP40s running at max plus 2 return pumps.
Nitrate: 0ppm
Phosphate: 0ppm
I feed only once per day currently New Era flakes. I only feed what is consumed and have a lot of critters that take care of any drop that hits the bottom.
Skimmer is Super Reef Octopus Cone with capacity rated almost double the tank size.
Photo period is noon to 10pm then moonlights on moon-cycle.
Tested the RODI, TDS its coming out 0ppm although for 2 weeks or so there it could have been maybe 2ppm before I replaced the DI resin.
I even syphon the stuff out when I do water changes.
What else can I do? I am tempted to do a 3 days lights out and water change at the end but also worried about loosing a bunch of SPS in the process.
I added some Purigen about 2 weeks ago and I think its helping but hard to tell.
Its done a lot of damage to my German Blue Digi
On another note I started running Carbon 24/7 (BRS Rox) about a year ago and I have had more coral disease this year than ever before. :/