Originally Posted By: catmandoo
Originally Posted By: BrianL
Originally Posted By: catmandoo
We've seen a small number of kills here in the last several weeks. I attribute it to pond turnovers. The top several feet of our pond and small lake thermoclines are in the mid-80s. I haven't measured lower, but I'm guessing that below about 5'-6', the water is in the 60s. Every couple of days we've been getting 2-4 inch thunderstorm rainfalls with really high winds that drop our air temps from the mid-90s to the low-70s in a matter of minutes.



That kind of weather is somewhat normal in NE Texas. I measured my surface temps down to 2 feet and it was 94 degrees. Several rain storms later within a couple weeks it was much cooler(I just did a stick my hand in for 2nd water test) guessing mid 80s. I wondered how this would effect my pond/fish. I did see two dead CNBG, before the rains, but that was it.


It depends on a couple of things. Your pond basically stratifies into three layers. The sun heats and helps oxygenate the top several feet. The bottom layer gets a lot less sun, so it is heavier, much cooler and has far less oxygen. Plants and fish usually can't live there. In between is a transition layer.

Strong winds cool rain can cause the pond layers to literally turn over. The temperature shock and change in oxygen can be lethal to fish, especially the larger fish.


Don't forget about the Hydrogen Sulfide that is also mixing in the water column from the anoxic bottom layer. If that is abundant enough, it can kill the fish even if there is enough O2 in the water, and it doesn't take much H2S at all to kill them.

Last edited by esshup; 08/05/17 11:03 AM. Reason: Changed H2S per John F. Thanks!!
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