Pond Boss Forums AERATION Systems questions Aerator Run Time

Hi. I have a 1 acre oval shaped pond that is 16ft deep across most of the center. I have 2 bottom diffuser aerators installed, equally spaced across the deepest part, which have been there for 5 years now. Normally I run both all summer and then only run one in the winter. I'm now getting some different opinions on this. My pond maintenance guy highly recommends I only run the aerators at night during the hot July/August time frame, but then I've had others in the industry say to keep running 24/7. I live in western Iowa and it can get really hot and humid here. The pond is also serviced by a deep underground well, kept relatively clean, seems healthy, and I've never had a fish kill (at least not floaters). Appreciate your opinions.

Both opinions are correct!

I know that sounds like a stupid answer, but there are a lot of trade-offs that are difficult to evaluate.

Cooler water is always capable of holding more dissolved oxygen than warmer water, so that is the first trade off. However, you have to circulate the water to keep it well oxygenated - and "de-stratifying" your pond increases the average temperature during the summer.

Dawn is usually the low oxygen point for a pond and also usually the coolest time of day. You better have good oxygenation beginning at some point prior to that time! That is either run 24/7 in the summer, or let the hot surface water radiate and have evaporative cooling for some period of time after sun down, and then have your aeration system kick on after x hours.

Every pond has a different configuration, different plant community, and different oxygen consumers in the pond. I would say the best way to determine the optimum for your pond is to buy a very expensive dissolved oxygen meter, and takes lots of DO and temperature measurements throughout the year. However, that is a ton of money and work.

The next best way would probably be to take the advice of a local expert. If you have a smart pond maintenance guy that also does a lot of other ponds in the area, he should have a good idea what will work for your area.

I like asking tons of questions (on any pond topic) on this forum. If you learn the reasons for the trade offs, that will help you make a good decision on the few times where something about your pond will make it the exception to the local prevailing wisdom. There are definitely some aeration experts here that can give you excellent general and regional advice.

Good luck taking great care of your fishes!


P.S. Where can I get a GSP that points walleye? I can think of many times that would be very helpful!

I would say don't mess with success! Others closer to your geographic area may have better opinions, though.

I am running the same scheme as you are doing, albeit I am only one year into being a pondmeister. I run one diffuser in winter, but in 3-4' of water to keep the immediate shoreline ice-free. I am pretty sure that one shallow diffuser still circulates the entire BOW to a constant temperature.

My only deviation is to turn off the system from 3pm-7pm when the electric company charges a higher rate!

Is that the norm? See my measurements. The yellow curve is before aeration, and the red curve is 2 weeks later with aeration. The uniform temp after aeration is about 4 deg F cooler at the shallow temps.

Edit: An average of all temps through the entire water column is essentially equal. 74.7 vs. 75 deg F.

I would guess your fish population matters the most for this question. If your fish are heat tolerant varieties, I would guess running 24/7 might be the more beneficial strategy. If you have less heat tolerant fish, then limiting the aeration during the hottest periods is likely the way to go. I personally have YP, SBS, and RES in my pond with seasonal tilapia. Bill tells me that the younger perch are more tolerant of heat, but as they grow larger (think ~14+") they become less tolerant of the heat, to the point that he has found some fish losses during those hottest days (and he's 3-4 hours north of me). To help combat this, he worked out that with my diffuser set up that I should achieve around 1 turnover for an hour of run time, therefore I run my diffuser for 1 hour over night. This allows my surface water to be as cool as possible before mixing, ideally allowing a little bit cooler escape during those dog days of summer.

Depending on your plant life and such, I've also been told you typically don't need much aeration up to around 6-7' as enough light should penetrate that deep to sustain plant life that will provide oxygen. I would guess pond dyes, turbidity, etc. would change that depth range.

I did take some temperature measurements last mid-summer, still running the aerators 24/7. As I recall there was very little temp difference between a foot down and just off the bottom. My fish species are walleye, yellow perch, and hybrid bluegill..and 2 grass carp. I also only stock minnows, no artificial feed. They seem to be healthy, my fish finder surveys are always productive.

Thank you Knobber for posting that graph.


This is my point when I hear of people saying "Only aerate when the air temps are cooler or the water will warm up in the pond". When I say "O.K., prove it" all I hear then is crickets.

I was told to do that many years ago when I wanted to keep trout longer into the summer in my pond.

So I did it and the trout died within a week. I ONLY ran the aeration system when the ambient air temp was below 70°F (I had a temperature controlled switch that only turned on when the temp was below that temp).

Next year I didn't aerate at all, and while the pond set up a thermocline at 8', the trout lived longer but still not all summer.

So, that's why I say that aerating only at night when the temps are cool is an old wives tale and it doesn't make a whit of difference in overall pond water temp if aeration is done during the day or at night.

Now what DOES make a difference is aerating at night to keep O2 levels higher. Personally, I run my aeration system in my personal pond 24/7 when the water temp hits the upper 50's in the Spring until when the water temp drops to the upper 50's again in the Fall, then only run the winter AirStation once the pond gets a coating of ice and snow.


Commander, I would ask your pond guy if he's ever done a detailed water temperature profile in a pond where aeration was done only at night when it was cool vs. 24/7 and if he says yes, ask him to email you the data. I'd be curious to see what the data looks like.

Thanks for the interesting reply. I believe I was told in the past that once a ponds oxygen saturation level is reached it will bleed off any excess. So if I've been running routinely 24/7 without any issues I think I'll just continue to do that.

D.O. and saturation are 2 separate things.
There is a point at a certain temp where saturation will not be above 100%, but also below that temp can be way above 100% in saturation. You can have low D.O. and still have 100% saturation depending on the cause of low D.O.