according to the experience of the guy in the following web page, Mardel Lab's Maracyn is super effective to address blue-green algae.
http://www.thekrib.com/Plants/Algae/cyanobacteria.html
please let us know the result if you tried. I am curious.
http://www.thekrib.com/Plants/Algae/cyanobacteria.html
please let us know the result if you tried. I am curious.