I've been fighting this crap for 3 months now, just stump on what else to do my 60G Cube Dominate with SPS It's mostly on the rocks a tad bit on the sand bed but nothing to cover it up. My MH lights are about 5 months old and I keep them on 7 hours a day. I am running GFO and Carbon change it out 3 times so far still getting the same results. I might switch back to Bio-Pellets. I am dosing 2 part using nutrient element source as they call it (Balling Light Method). I think this may also be casuing some of my Cyano issues.[/QUOTE]
How deep is your sand bed? I ran GFO\Carbon since day one, at some point switched to the high capacity GFO, started doing 30% water changes weekly, and after months got it down a LOT (cyano that is). I just couldn't ever get rid of it. I finally broke down, did chemi clean, and literally overnight it is gone. I have a small patch on one part of the sand that is contained and is being managed. I actually always said before I even did the chemi clean I will end up doing more than one dose because of the severity of the problem.
I started doing some reading on sand beds and I think my sand bed is the culprit of my issues. It ranges from 3-4" (wrasses and clowns kick it around constantly). Read this...
Deep Sand Bed depending on your depth, but mine is basically a DSB... on the lower end of it at least. So what I noticed was this..
What my sand used to look like from a cross section
To what it was at the WORST of my struggles with cyano
In my case, my theory is I simply overwhelmed my sand bed, rendering it rather useless for quite a while which caused my issues. With GFO, huge water changes, careful feeding, etc it cleared up some, but after chemi clean two weeks ago my sand and tank look like this.. Notice how the cross section isn't just one block of red\green cyano colonies. My sides of the bed are actually completely white from back to front!
I don't mean to hijack your thread but want to give you my experience. Literally six months of HC GFO, Carbon, lots of salt, RO equipment and a lot of frustration. Chemi clean did more in one day that all of that did in months. Now I just work to keep it tidy and am not climbing a straight uphill climb anymore..
Good luck, let me know if I can help, I just went through this.. it sucks.