My pond is approx 1/3 acre in surface area, it is around 18' deep in the center and is spring fed with no outlets or inlets. I have a windmill aerator that was just installed. The pond is 2 years old and was just stocked with fatheads and bluegill. I was just told that during the hot summer months the pond would stay cooler if cut the aeration to it and let the cooler water stay on the bottom as opposed to circulating it. Does this make sense???

Sure, the cooler water would absolutely be on the bottom if you cut off the aeration off. It will even be cooler with the aeration on. That's because the bottom is the bottom and it gets less sunlight than the top. Unless you've got diffussers all over the pond bottom, the bottom will always be cooler.

Not sure I'm understanding what you want out of this question. You purchased the aeration system to have better water, so why would you want to turn it off?

I really don't, but the guy who was telling me this was the owner of the fish farm where I got my fish, so I assumed he would know what he was talking about, even if it didn't make much sense to me. I guess I just wanted someone else's opinion (especially if it supported mine )

It makes ABSOLUTELY no sense.

Actually it does indeed make sense, but only to a point. If you use the aerator you will be moving the cooler water to the surface and as such it will start to gain the heat from the sun, air, etc. Thus you will indeed overall warm up the pond. If you don't aerate you will have a couple of things going on, you will have the temperature in the pond stratify. The cooler water will be down deeper and the warmer water will remain on top. You also potentially will have a situation where you may have a lack of O2 where the fish are and thus have a kill off.

If you had trout or some other cold water fish in the pond, I might understand better the advice to turn off the aeration system to keep the temperature of the overall pond from getting too high. However you said you had fatheads and bluegills in the pond and they have a fairly high range of temperatures that they can withstand. Thus I would keep the system going.

The wild card that is also in play here is that you said you have a spring fed spot with the pond having no inlet or outlet. This intrigues me, it would have to mean that either the spring stops during the year or is evenly matched to the evaporation/seepage of the pond. Otherwise you would have some outlet on the pond if the spring was continually adding new water to the pond. That being said, where I was going was that if the pond is spring fed you will most likely be getting colder water through the spring and that would help to keep the overall temperature of the pond lower even with the aeration system. Also note that being spring fed does not mean that the spring has enough O2 in the water to help out and as such you could be causing more of a problem to the pond for fish kills if you did not aerate.

I guess long and short of it is I think in your case you should aerate the pond. I think you will not have a problem with overheating the pond with waht you have stocked in there and you will have a healthier pond.

Yes. maybe I was a little too definitive, but no doubt the overall water quality and the fact that more of the water is habitable, at least in my case even in the warm south far outways any small increase in overall tremps.

Ahhhh Like everything in life there are no absolutes. ( Except maybe vodka ) anyway, as you can see for his application it would make sense to me as well to keep the aerator running. But everything has to be looked at carefully to come to the right conclusion to a persons application. I might not give the same advice to someone trying to raise trout, but then again I think I would need more information as to where the spring is going if it is not exiting the pond and how cool the spring is and how much O2 is in the water from the spring.