cd5 the best thing you did was switch to ro
If your showing any PO4
you have enough for cyno to grow. Figure that the cyno is using po4
to live so you won't pick up what it is using. You need to get it to 0 if you still have cnyo. I battled this stuff on and off for a year and it only went away when i added a phosban reactor and got all new ro
filters. I ran phosban in the bag in my sump for months and it did nothing till I got a reactor....
Good luck with the battle..