This is the second year in a row that when October came I lost all of my fish in my pond. Last year I believe it was a lack of oxygen as I saw them at the surface of the water a lot and their gills looked bad. This morning I woke up to three dead koi and three dead goldfish. My water seems incredibly dirty all of a sudden (clear yesterday). The bubbles on the surface are suddenly thick (I can push them around with a net). Ammonia was 0.25 nitrate and nitrite were both 0 and ph was 7.8. One thing I did notice was that overnight one of my solar lights fell off of the tree and into the pond. There wasn’t much to the light (small solar panel connected to leds) but I feel like this would be too coincidental to not be the cause. I’m not sure what my question is exactly but I’m hoping to learn something to avoid this next year. Could whatever chemicals are in led solar lights kill all of the fish and also result in this extra thick foaming on the surface. Is there something I could test for to find out if it’s something I’ve done wrong. Please help.
~1600gallon pond, also it appears as though any other life in the pond has also died. (Worms are floating around and were found dead on the rocks around the perimeter of the pond).