I had a biologist come out today. He checked DO and temp and said the whole pond was uniform top to bottom. I showed him the chemical I used on my lawn and we saw that in addition to 2-4D there was another chemical in there so he checked with the EPA and found out that the stuff I used on my lawn wasn't the problem. I have three field tiles that drain into the pond and he thinks this could be the problem. I have my doubts because this time of the year there isn't any chemicals being used on the fields. Also it only seems to be mostly perch, walleye, and minnows dying with a small percentage being large mouth bass no crappie or bluegill. The biologist looked at some of the dead fish and they appear to have nothing wrong with them. He would like to send a fish to be tested, so I found one that wasn't quite dead yet and put it on ice.