Cyano only grows on tops of rock

[NedFlounders]

I"ve been dealing with a bit of cyano lately, but only on the tops of half of the rock in the tank, never on the sand.

According to Hanna, there is 0 phosphate and Red Sea says <10 nitrate ppm. I feed about 1/4 of a brine cube twice per day with the small addition of tiny pellet food in the evening. It is all consumed quickly.

I've done the 3 day lights out trick. I've also used chemiclean. It keeps coming back!

I do 20% weekly water changes and syphon the cyano weekly.
I have a Kessil A360w that's on for 11 and off for 13, only using blue lighting with intensity never above 45%.

I run a carbon reactor, GFO reactor, as well as a skimmer, AND a refugium.

The refugium definitely slows the spread of the cyano, but it's never eliminated.

Am I missing something here? Consistently testing parameters incorrectly? Not sure why I still have this problem...:\

 

[cloak]

What are you using for flow? Maybe that's just a dead spot where the bacteria is able to grab a foothold so to say. Only using the blue lighting may have something to do with it as well. Picture?

 

[ryeguyy84]

how old is the tank?

 

[NedFlounders]

The tank is 9 months old. Here's a shot of the cyano..

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[MadCnty]

Vacuum it off, and gain some more flow should help if your numbers are correct... And as cloak said adjust your lighting... I replace my bulbs every 6 months just to be on the safe side...