How did I control unstoppable mass mortality of big fishes in a large deep pond?

Magnitude of the problem, Fishes which were mostly affected, Background of the pond. Stocking and feeding methods followed. My investigation started. Observations on water parameters. Observation on plankton level of water, Observation on pathomorphology. Trying to find out reason of mass mortality of fish. Symptoms of nitrite toxicity. Mechanism of detoxification of nitrite. Factors affecting nitrite toxicity - Duration of exposure, Oxygen, Temperature, Fish size and age. Recommendations given, Mass mortality of fish was stopped. Date of application of salt. Procedure for application of salt. Effect. Management measures taken to reduce the incident in near future. Management measures taken to reduce the incident in near future. Last words.