Yesterday we had good weather, so I put out my fish from the indoor 75 gallon tank into a 125 gallon pond. Pond is clean no sludge. It has a good filter.. I put out one 8 inch large fan tail gold fish had her for at least eight years, and about 6 four inch fancy gold fish.. The 125 gallon pond had three small goldfish that had over wintered in the pond... Our day temp was 85 and night was 48 degrees. I did a small water change added in some Pond Prime. I covered the top with a new pond net. This morning all my fish but one was dead including the ones that had wintered in the pond. The one that survived was one of those that wintered in the pond. He is now inside. He seems fine. All fish were found dead lying on the bottom. Not floating on the top. I took a water sample to our pond Shop and my water was good. What happened? too much Prime?? I do not recall putting too much in..Had nothing toxic on my hands. Worried about the new net having a toxin. I changed all the water, put charcoal, and added two little feeder fish. I am scared to add in anything.. Did I add too many fish at once? I learned a lesson next time go out hour on the hour and check that added fish are doing fine. If I had only caught them early, maybe they would be alive.