I get that @jaypeecee but your opening line in this thread was this.Thanks for the feedback.
I don't think it's as simple as X causes Y.
I'll suggest they also need a number of other nutrients to survive, omit any one of them and the cyanobacteria will reced.Based on a lot of observations and measurements, I'd like to put forward a suggestion/hypothesis. It is this:
Perhaps cyanobacteria (BGA) and algae need inorganic phosphate (orthophosphate)/PO4
Maybe this hypothesis is above my head (which is probable) just trying to understand what exactly it is you're suggesting is the cause of algae/cyanobacteria.