My pond isn't that old, so not sure this is really a change in trend. Put aeration in this year, been working well by the parameters we look for. The stratification was non-existent this summer. Generally 4-5 deg difference across 15' of depth.

It seemed the pond cooled off very quickly this fall. This weekend, the water was down to 46 deg. We've not had night time temps that low yet. Still some 80s for highs. I'd been backing off feeding length, but this weekend, they just weren't interested so I pulled the battery out of the feeder and shut it down for the season. BG quit spawning long ago.

Only thing I could think of is the bedrock under the pond has cooled and with the reduced sunlight in a wooded ravine, water took on the earth's temperature more than air temperature with a complete turnover every day.

Seemed awfully early for water to be so cold and the fish reaction to normal feed times was just meager. Can aeration really drop mean water temp over leaving it stratified and thus a shorter season?

This is interesting. I hope to add aeration next summer. Looking forward to the replies on this one. My pond is in a wooded revine also, and heavily shaded. I never really see very warm water temps. I could very likely have the same scenario when I start aeration.

isn't 46 degrees below ground water temp? How does that happen if air temp is warmer than ground water temp and you are aerating? One experiment you could do is only aerate when air temps are warmest. I have a timer that helps with making that switch easier (summer aerate at night to prevent warming of the water, fall switch to the opposite)

If you have 80s in the day I can't imagine you wouldn't warm up with aeration.

I'd double check the thermometer. 46°F is roughly 10 °F cooler than groundwater temperature there.

Did you get a heavy, cold rain?

Almost seems like that HAS to be a bad temperature reading. I am not all that far from you and we are nowhere near that temp in our BOWs. BM61.

I guess this could be a good learning opportunity. supercooling with aeration is possible with cold air temps.

I'm sure the WI and northern MN ponds still have ground water temps around 50 even in the dead of winter. The question is what is an expected differential between ground water and pond water using only aeration as your cooling mechanism?

of course a pond with inflow from a stream or creek would be very different than a 'sealed' pond, and a groundwater pond with some inflow/outflow of water through the bottom of the pond would also be a a factor to consider.

Your ground water temperature in S. Indiana should be at 56-57 degrees F. Ours is around 62 degrees. Central Minnesota is 42 degrees.

Dan, you know my ponds and the proximity to yours....my water temp as of this evening is 68 degrees. And I have been aerating 24/7 since early spring. Something has to be amiss.