Scott, I fear that blue-green algae (BGA) is not just a hazard to the fish. BGA gives off BMAA, a neurotoxin strongly associated with dementia caused by brain plaques in mammals. That includes humans.
I'll link to a recent article about research on the subject. Best advice: treat BGA aggressively & early, don't eat fish from a lake with BGA, and don't swim or wade in it.
By the way, if someone is exposed to BGA, they might consider L-serine supplements. Cheap insurance.
https://www.washingtonpost.com/local/soc...a902_story.html 
