Pond Boss Forums GENERAL QUESTIONS Water chemistry FISH KILLS/LOW SALT LEVELS

Depending on the stocking and initial survival rates the deaths could be nature's way of thinning out the weakest individuals from a community that is too abundant for the recent food supply. I suspect that the predators are eating lots of the weak and dying fish and you are seeing the surplus that they are not able to eat. During cool weather (winter) the food levels are usually at year lows for smallest fish in the pond. I suspect that some or a bunch of smaller fish went into winter hungry, are now succumbing to starvation after a winter, low food, stress period. Fish usually need a fair amount of body fat in fall the make it through winter in good health.

Salt concentrations can get pretty high before salt will start affecting the overall health of your pond fish. I doubt very much that salt has anything to do with the deaths unless your salt levels are close to that of sea water.