Pond Boss Forums MANAGING AN EXISTING POND Evaluating and adjusting fish populations dying fish

any sign of fish on surface gasping for air?? if so could be oxygen depletion which can kill fish - however I believe when that happens it is a sudden die off as opposed to a few fish dying at a time. I lost all my fish some years back due to sudden cooler weather following a drought and the lake turned over and my fish died from lack of oxygen.