Convinced of a link between GFO and Cyano (and not the good kind)

[MitchM]

Originally Posted by Myka

... Anyway, the reason the cyano appears is because the water column is suddenly barren of phosphate yet the substrate and rock is still loaded. As the phosphate leeches out of the substrate and rock the cyano jumps in to feed off it as it leeches. Cyanobacteria are extremely efficient at processing phosphate.

....

Right. The cyano will also appear on dying macro algae.
You'll still have to siphon the cyano out as it appears, if it does.

The key is keeping phosphate out of the water column in the long run. I'm finding it easier to dose Foz Down, it's a lot less hassle than GFO and I can instantly tweak the dosing to match my feeding schedule.