The reason for the fish kill is the pond iced over and was snow covered almost all winter. I should have shoveled off a lot of the snow so the sun could have produced oxygen to the submerged plants. For 15 years the pond iced over most of the winterd but we never had a constant covering of snow like this winter in eastern Indiana. It was a wonderful pond but now I'm going to change to a minnow pond and play it from ear after that. But why aren't my GS along the edge of the pond?