Originally Posted by Biergott
So maybe I had the 1-2 punch of bacteria followed by green algae.
Both can be fueled by excess nutrients in the water. The bacteria live off Ammonia and Nitrite, the algae lives off all three nitrogen cycle compounds. Your water quality readings may still look ok if the algae/bacteria currently have all that nitrogen locked up, and this condition does keep the situation from becoming toxic, but there is still a spike in nutrients causing the problem.