Hi, j. Sorry for your loss.

What I don't see mentioned here is filtration and aeration. Is your water being circulated & filtered adequately? Fish listing near the surface can be a sign of oxygen depletion, however, your inspection of the fish may indicate otherwise. Water temps can also be a contributing factor in above ground ponds. I see you are in zone 9.

Were any new fish quarantined before adding to your pond? What was the source of the plants which you suspect babies hitched a ride on? We they transferred from one of your other ponds which you deem to be a safe environment or were they from an outside source?

All things to consider. Not sure what your definition of a 'small amount of gravel' is (and I certainly don't want to resurrect the gravel v. no gravel debate) This may or may not be a contributing factor depending on your setup.

Hopefully, someone else will be along shortly to help you with the specific symptoms. It always frustrating and sometimes heartbreaking when things go south. Such is the life of a ponder. I hope you get your answers soon so you can correct the problem.

blessings,
~digger

Hi Digger: as to filtration and aeration, I have a pump with two spillways/bulkheads for aeration, and for filtration, I use heavy planting: water lily, anacharis, cattails, arrowhead plant, water hyacinth, water lettuce, parrot's feather, azolla, and one other flowering plant I can't remember the name of.

As far as water temp, it's been in the 70s and low 80s outside for a few weeks, was on the hot side before that, but the water temp never got over about 82 as I measured it.

I have not added fish since I initially stocked it, and the eggs came via plants from one of my other ponds where there have been no problems.

There really isn't much gravel at all and it is in a very sparse single layer, and only in some places.

All that being said, there were no dead fish today, and the one black moor who has been on the floor of the pond for a week took a turn around the pond at feeding time, which was very encouraging. I am sure the neighbors were confused about the giggling and hand-clapping when I saw him.

The remaining fish (with the exception of one baby shubunkin) are now active and normal looking.

And just to make it all slightly more vexing, I saw a new group of fry swimming around right in the midst of all of it.

I will keep my fingers crossed that tomorrow morning things look even brighter. Maybe the water change I did yesterday helped some. (?) Thanks so much for your generous assistance.

I wouldn't be surprised if the new fishies are the result of what caused the problem. If you have new babies there must have been a spawn which can affect all the fish in the pond, involved or not. Everybody gets excited even if it is just trying to get out of the way of the more aggressive fish or looking for a chance to gobble up some roe. Of course that is speculation.

Thank you for the update. So good to hear things are turning around for you. Best of luck with your newly discovered fry. Hope things are looking brighter now.

bless ya,
~digger

Could have been a spike in the water chem. Chlorine n the makeup water? cooties on the plants and such have been known to cause issues also. I really couldn't tell you as with koi it could be a number of things from parasites to water Chemistry. Spawning surly messes with the water chemistry. do you have a decent test kit.

Here is a link that might be useful: Die off

Hi Tuder: I do always add conditioner when I add water. I wonder if it is possible that I did not add it once. Of course, I never add that much water at once, perhaps 5-10% of total volume maximum. It surely has been a mystery. I have lost two more fish since my last entry, but they were "on the way out," by the time I made my first post. It has been a real mystery. Since then I don't believe that any fish have newly become ill. Poor sad quiet pond with so few residents, I had to go scoop up some minnows from another pond to fill the void. They are doing fine so far. :) And yes I have a test kit. The water in these ponds is always spot on.

If your tests are always "spot on" I would wonder if the tests were accurate. I get minor changes all the time. What kind of test kit are you using and how old is it? How is it stored?