I don't see how I can have excess nutrients, only got 2 clowns and a yellow tang in my 260L, Nitrates undetectable. Have a 50L sump with skimmer and chaeto in it and phosban 150 reactor with phos/carbon.
Oh also, I have no algae in my tank either.
Also what is GFO?
GFO --- is basically any iron base phosphate removing media (( I can't recall what the "G" stands for --- believe the "F" and "O" stand for ferric oxide )).
I use RO water and a DI pod yeah, TDS 0. Phospates read 0, I use the D&D merck test kit.
The only thing that changed is I went to a new bucket of salt, D&D's H2Ocean Pro, it came up after I switched to it, possibly that's the source? But I find it hard to believe a salt will cause Cyano.
G stands for Granular