Well after 4 years I finally had a fish kill but don't know why. My pond is about 1/2 acre, 17 ft deep in the middle, about 30 years old, BG, BCP, and LMB. I stocked 25 LMB 3 years ago due to not catching any and having a LOT of BG. I have been stocking TP the previous three years but have not this year. I do have a lot of FA and Chara.

I'm trying to figure out why this happened. I do aerate from around midnight to 8am. We have had a lot of rain this spring and the pond has been going over the emergency spillway. Recent rains have knocked down the FA. Could that have caused a DO crash even with the aerator running?

Tonight I scooped out around 100 BG all sizes, 2 small LMB and 7 2-3 lb LMB. There are about 20 - 30 more BG that I couldn't get to. Should I turn on the Aerator 24/7?

Well I decided to go ahead and turn the aerator back on. I figure it couldn't hurt.

Thanks.

During the summer I will turn my aerator on 24/7 when we have a bout of cold rainy weather that lasts for several days.

I am trying to find out if there is any research on how pesticide drift might effect algae blooms and cause a DO sag. Dicamba is very volitol and can drift for miles under the right conditions, sometimes it's mixed with other pesticides.

https://www.independentsciencenews.org/e...-worse-in-2018/

Is it possible that the original stocked fish (and added LMB) have grown to the point that the pond's carrying capacity was achieved?

Just a thought that runs through my head as I watch my fish grow (year two) and try to plan my culling efforts.

Running the aerators more sounds like good insurance, just watch your water temps as summer kicks in so that you don't over heat the pond. Warmer water carries less DO. I can't prescribe the balancing act here, but I can say that I TRY to keep my pond from getting warmer than 85 degrees F at 18 inches below the surface.

Rain will usually knock the FA in my pond back down below the surface, But I think it rises back up. I don't let it stay in the pond if I can help it. I rake it out.

Here are some questions to answer that may help others with more experience add to your thread...

1.) Can you estimate the numbers of fish and types with average sizes that are in the pond? Ultimately, a total number of pounds of fish in the pond would be good to know.

2.) Describe your aeration system...pump size, diffuser type and quantity, & diffuser depths.

3.) Any water chemistry that you have available.

4.) Water temps throughout the column.

5.) Are Turbidity/Clarity measurements available?

6.) chemicals being used around your property (fertilizers, pesticides, herbicides)?

7.) Are there any signs of illness/stress on the fish?

That's all I can come up with at this point other than the benefit from losing several pounds of fish IF it was a DO crash is that there is less biomass for the pond to support now. That may not be very comforting, but it does lessen the likelihood of it happening again right away.

Sorry for the delay on any update. I've been busy trying to clean up the pond. In total I have removed about seven 5 gallon buckets FULL of fish. All different sizes, mostly BG and LMB. There where very few BCP, about a dozen. Things I noticed during the cleanup.

1. The water is very murky. Typically my water is very clear. It went down to 10" of visability and now it is about 20".

2. While in the pond I did notice quite a bit of black nasty bits along the pond edge and on the weeds.

3. Bad smell. Not sure if it's all due to the rotting fish or the black sludge.

4. I did notice large schools of fry swimming while cleaning up the dead ones on the first couple of days. I didn't see them yesterday but I will check tonight. I have not seen anything larger.

5. I still have several bullfrogs and bullfrog tadpoles. Didn't see any dead ones.

So here is my theory. I don't have data to back it up but .....

My pond is 30 yrs old. Aeration was added just before I purchased it in 2014. The aerator is a Gast 0523 (4.0 CFM @ 10 PSI) with only 1-9" diffuser at the deepest spot. The pond has quite a bit of leaf debris as the property is all wooded, I have removed most of the trees around the pond to reduce this. Every year the muck layer seems to be reduced. I also remove FA whenever I can. Each year seems to be getting better. Prior to this happening we had several cloudy days and then a heavy cold rain event. It looks to me that the pond turned over rapidly which caused the problem. I think what I am going to do is add another diffuser and run 24/7 until the water gets too warm. Would my pump handle two diffusers with one at 17' and 1 at about 14'? I have 3/8" sinking line.

Thanks,
GKLOP

I didn't see what diffuser you are using. Your pump could handle 3 vertex discs.

Just a thought...if your 1/2 acre pond is about one million gallons and your aeration system has been running 8 hours a day...you should have been turning the pond over about once in that 8 hour run. I would think that would eliminate the possibility of a toxic turn over, but you might have been on the cutting edge. Do you have water temps from throughout the water column?

Wbuffet is likely correct in that the 0523 can handle 3 vertex diffusers...depending on you setup. My 0523 pushes 3 diffusers, but my lines are 5/8" and the deepest setting is about 8 feet. My guess is that it will push 2 diffusers very well, but three might just be on the edge of good efficiency. Either way, I think spreading them out in the pond would still be a benefit.

OK. I got my second diffuser installed. The water is a good looking green and all of the smell is gone. Most all of the black crud is gone. I have tried fishing and and trapping and still haven't seen any indications of life, other than thousands of bullfrog tadpoles. Other than doing a shock survey what is the best way to find out if anything survived. If indeed there is nothing left should I wait until fall to restock with something?

I would do a seine survey to see if you have any small fish present.