I have a 1/5 acre pond that was dug last summer. it is clay soil. Max depth of 15 feet. In early May we put 40 perch, 50 bluegill, 10 sunfish, 10 crappie, and 2 male white suckers in there. I added an aerator a month ago with no problems. A week ago we had constant rain for 2 days. 4 days ago 38 of the perch and one of the sunfish were dead. The next day the last 2 perch, both suckers, and one bluegill were dead. No other deaths since then? Any insight into what happened? We checked the pH and it was 8.6.
8.6 is on the higher end, not sure if that was a contributing factor. Also, not sure what you mean by “50 bluegill and 10 sunfish” since a Bluegill *is* a sunfish. What did they have to eat? Were you pellet feeding? Did you first stock Fathead Minnows?
"In the age of information, ignorance is a choice." - Donny Miller
I heard of this happening as a result of a heavy rain before, which can cause a few things to happen: Big PH swings, big PH swings as a result of the loss of buffer calcium in the water (extremely soft). You may wish to add limestone (dolomite) to the pond to help prevent this in the future. The other thing that can happen is a quick turn-over of the water column bringing nasty anaerobic water up into the places where the fish live. Unlikely in a new pond though.
Sorry, sunfish is the regional slang for pumpkinseed. We had fathead minnows in there and the pond has a good supply of tadpoles and bugs so we were not using pellets at all.
Depends on the actual biomass present but anoxic water forms faster with many fish, plants, other organisms, etc.. In a fish-heavy pond (Carrying capacity is reached) it can happen fairly fast. Need to know what time of day aerator is being run? It sounds like you had a hypolimnetic situation in place and possibly the aeration system wasn't strong enough flow to mix it, but the heavy rain most certainly was.. Rain is "usually" slightly slightly acidic (below 7.4). Run-off, depending on what it flows over before entering the pond, can cause yet other issues. Perch (yellow) tend to handle slightly less O2 than some species but there are other factors. Pumkinseed I don't know much about yet so I'll reserve that for others in the know.. Not knowing how you started up your aeration and it's capabilities, I "think" your rain event could possibly be the culprit.
It's best to run the aeration at my pond 24/7, but some, maybe most, ponds can do with less. There's a lot of variables to know for sure without testing your particular pond's environment. I'd say, in general, running a properly sized system 24/7 is best, but may not be a necessity.
Luckily at my pond, when I get a lot of rain (spring and fall) that causes excessive throughput...the rain temp and pond water temp are very close to the same. But, if the temp difference is large enough along with any chemistry differences this can cause stress to the fish.
An undersized aerator can cause problems given that it is not moving enough water to eliminate all the dead water at the bottom. A fresh and large inflow of rain water of a different temp than the pond water can cause the pond to turn and the dead water mixes in too quickly. This would be hard on the fish.
