It definilt is cyano, but it also looks like there's some dinoflagellates in the picture as well or maybe I just forsee what's coming lol. Nutrient levels too low, zero nitrates and phosphates are not good. Especially adding more gfo, I've battled this stuff multiple times and dino as well. Back and forth for months between the 2. Finally realizing after lots of reading on here that I was trying to remove nutrients i didn't have causing the problems with cyano and dinos. I stopped running gfo, stopped doing water changes for a couple weeks. Allowing the nitueint levels to rise. I also dosed flourish phosphorus by seachem to get my po4 to a detectable level. Once I did that,I manually removed everything o could by hand and then used chemiclean per the directions for 2 days. After that I performed a 30% water change and ran carbon to remove the rest of the chemiclean. I feed heavier now and maintain detectable levels of phosphates (0.04-0.10) and nitrates between 4-8. At those numbers I have been cyano and dino free for about 6 months so far.
I didn't do a black out bc I have alot of coral and I didn it once before and bleached and stressed alot of coral.
Hope this helps.
Short version
..
High current water flow in tank, detectable nutrients, stable lighting less red/green spectrum if possible, dont run gfo if you can help it, run chemiclean per instructions and run carbon and water change after 3 days. feed heavier and do less water changes until system is stable. Then resume normal water changes and feedings.
I didn't do a black out bc I have alot of coral and I didn it once before and bleached and stressed alot of coral.
Hope this helps.
Short version
..
High current water flow in tank, detectable nutrients, stable lighting less red/green spectrum if possible, dont run gfo if you can help it, run chemiclean per instructions and run carbon and water change after 3 days. feed heavier and do less water changes until system is stable. Then resume normal water changes and feedings.