Pond Boss Forums GENERAL QUESTIONS Water chemistry Fish Keep Dying

Have a 1/3 acre pond and completely separate independent pond that is only about 20 ft by 40 ft. This is my 3rd year on this property. The fish have been dying last several days and I cannot figure out what is the most likely cause. I have left pump/waterfall on continuously to make sure the oxygen levels are high. There is a lot of plantlife in both ponds and there has been a lot of sun so I don't believe oxygen to be the issue.

I got one of those cheap PH testers but its too inaccurate for me to figure anything out.
Decent amount of leaves tend to get in the pond during the fall. However, this has not been a huge issue until this season (again my 3rd season here). There is also a cottonwood tree that rains hell down on these ponds. When I first arrived there were 3 of them so I'm down to just 1 now.
Looking for any input on what might be the likely cause. All types of fish in the pond are dying LMB, BG, CC, Feral Goldfish.

Appreciate any help!

Are they dying in both ponds? Have you had any heavy rainfall recently?

Dying mainly in the bigger pond. 2 died in the smaller one and the smaller one is encased in concrete so no ground runoff would get it, although obviously tree leaves still can. I don't think the rainfall has been that out of the ordinary

another point maybe worth adding, the pond water seemed kinda darkish in color. 2 months ago it looked very clear so that is a change. Not really muddy, just darker tinted. Its what made me wonder about the leaves since the temperature outside kinda got hot quickly and it seemed shortly after is when the fish started dying.

1) Are/were the fish "piping" (gulping air) at the surface?
2) Was it the larger or smaller fish that initially died?
3) What was the water-clarity? Was a strong plankton bloom present?
4) Weather conditions: Sunny? Cloudy? Any heavy rains?
5) If any recent rains occurred, is there anything suspect (especially anything new) located within the pond's watershed?

Kelly,
1) They are not gulping for air. I have seen this in the past and turning the pump on has fixed it. This is something different.
2) Big channel catfish and largemouth bass as well as bluegill all seem to be dying intermentently. I.E. Size doesn't seem to matter on who dies first.
3) Water is Darkish but not muddy. Water was pretty clear month or 2 ago and temperate kinda heated up and now its kinda dark in color, almost black but not quite that dark. Visibility is pretty limited through water due to this darkish tint. I've had a lot of green surface algae on the surface before but not a whole lot currently.
4) Weather has been hotter and decent amount of sun with some clouds and rain.
5) Both ponds are stand-alone. The smaller one in elevated and encased in concrete so no water runoff would get into it from rain.

I will say though based on fish population the large pond has a lot of bluegill. I would say it's maybe 80 to 90% bluegill. If I had to guess I would say only about 60% of the dead fish are bluegill though. Every day there's about 6ish that are dead.

1) Do you, or have you been feeding the fish?
2) If so, are they still actively feeding?
3) Do any of the dead/dying fish show any signs of disease or internal/external parasites?

I have not noticed anything odd about the fish that have been dead. I was feeding them but havent lately as they dont seem as interested other than some bluegill.

I saw a small pond that had a large top of an Oak Tree fall in it, and the leaves were green. After about a week the water started to turn black and smell. I hurried up and pulled the tree out of the pond and turned up the aeration system to the pond. Only a few fish died, but I was concerned that the whole pond would go. I just think I got lucky and barely saved it.

If it smells, the water quality is going down the tubes fast. More air, LOTS more air and try and figure out what is getting put into the pond to make it smell.

Excess nutrients? Water warming up and not holding as much dissolved O2 as cooler water? If the BOD is high, the increased water temp could have tipped the scale to an anoxic event. How big is the BOD load on the pond?

Acronyms:

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=92442#Post92442

Kobe - If they're not piping for air and otherwise dying in small numbers over time, I'm guessing DO isn't the problem. Likewise, a lethal toxin-introduction or pH condition would probably cause a more acute and large-scale response.
My layman's hunch is that a disease or parasite is involved.
It might be worthwhile to collect a fresh-dead specimen and put it on ice for transport to the nearest university or some other entity that offers disease/pathogen forensics for fish.
Maybe some of the professional fishery biologists (which I am not) will have other suggestions. Good luck.

Can you post a pic of the water and a dead fish ?