Two years ago I built a pond in my yard. A friend of mine gave me some koi and when winter hit they didn't make it. It appeared as though some sort of parasite had gotten to their gills and killed them. Unfortunate and upsetting to say the least. Changes were made to avoid the same happening this year (Keeping the UV on further into the winter, adding a bubbler to provide more oxygen into the pond).
This year everything was going great, beautiful 12+inch koi, a few goldfish. Everyone was happy (myself included). Cleaning the filter weekly, UV was on, bubbler runs all day long. Went to bed last night and everyone was fine, woke up this morning and every single fish (I'm assuming, I still haven't found one) was dead.
No sign of parasites that I could see, the gills looked healthy upon inspection. We had a relatively large rain storm last night but nothing more than I've seen in the past without effecting the pond negatively.
Nitrate: 0, Nitrite: 0, Ammonia: 0.25, PH: 7.8, ~1600 gallon pond, 3 Koi, 4 Goldfish
The few interesting things to note. This morning was the dirtiest I've ever seen the water, as if the storm kicked up a ton of junk from the bottom. The bubbles on the surface are no longer simply air bubbles that go away quickly but rather thick foamy bubbles I can pick up with my net. It has a greenish tint to the bubbles as well.
Coincidentally (or not) one of the solar light fixtures I had above my pond was taken down by the storm as well and I found it inside of my pond. Not sure if they are toxic or not but it was a relatively small solar panel with a small string of LED lights on it.
I didn't see much odd behavior occurring before this incident, the Koi would occasionally hang out looking at the waterfall but they weren't gasping at the surface so I didn't think much of it.
There's a tree hanging over the pond that drops seeds this time of year, sadly I'm not sure what type of tree it is or if it could be the problem but I thought I'd mention it as well.
Another interesting fact is that it appears as though anything in the pond (with the exception of plants) has died. There were a number of worms floating inside of the pond, laying on nearby rocks, scooped up with the net. Something horrible happened last night and I'm at a loss for what it might have been. I need help figuring out what went wrong before I give this a third attempt. I don't want to be the person who just keeps putting fish in and hoping for the best without at the very least feeling like I have an explanation for and guard against what has happened to me.
Please help me understand what went wrong here. I appreciate any and all feedback.