As a pond algae specialist (we all have to grow up to be something right?:) I make a point to keep tabs on the various happenings around the U.S. on algae and came across this article on a recent fish kill in a community pond.
This is just one incident that got publicized somewhat, where many others simply go unreported, but let’s just say that mid-summer fish kills aren’t all that uncommon.
High temperatures are largely to blame because once you see air temps getting into the high 80’s and beyond, it’s a fairly good bet that in some ponds the water temperature will be near or above 78 degrees and that’s kind of a magic number. Higher than this and the water’s ability to hold on to dissolved oxygen will begin to drop and DO is critical to fish health.