I have posted under the "Help" section of the "General Questions" about a recent fish kill that took out all of our fish in a 10 acre 55 year old pond. Here are the water test results from a sample I sent to Oklahoma State U.
Any thoughts or ideas?

Here is the water test info:

pH 8.1
EC 2790
Sodium ppm 337
Calcium ppm 223
Magnesium ppm 54
Potassium ppm 10

Nitrate-N ppm <1
Chloride ppm 321
Sulfate ppm 964
Boron ppm .096
Bicarbonate ppm 112

Total Soluble Salts TSS in ppm 2020.9
Sodium Adsorption Ratio 5.2
Potassium Adsorption Ratio 0.1

Sodium Percentage 48.5%
Hardness ppm 779
Alkalinity ppm as CaCO3 91.8

Western Oklahoma. 15 acre 60 year old pond. Well established with fathead, bluegill, bass and a few large catfish. Aeration in the deepest (14 ft.) 1/3 of the pond. Most of the pond is 6 feet. Feeder.