Why not run aerator 24/7?
Answer- there are times and nights when the air temps are 75, 80, or even 85 degrees. Anytime you run a trout pond aerator when air temps are that high, you are convection warming the pond. If the bottom water temp is 68 and the air temp is 80, you will add max. thermal energy into the pond- bad idea. We could have safely run the aertor ON when it dropped below 68 and off at 70, but we wanted max. cooling times.
We ran aerator 24/7 4 years ago when we first stocked rainbows and the temp lept rapidly rising and by July 4th it reached 75 degrees and allthe trout went psychotic (circling like sharks) and died within a few hours. Steep learning curve in this.
What I've learned is to first protect DO levles and a close second- protect water temps.
We measured as high as 73 at the BOTTOM during one week in the deepest areas. That was pretty scary, as trout most often don't survive after 70-72! It is likely that the newly installed well pumping another 20 gpm of 48 degree water was creating some coller pockets where they hung out. Also- since the aerator was working more than half the days, we never had only a little stratification. During one hot period, it was 72 at surface and 69 on the bottom-fyi.
Finally, summer DO levels were measured infrequently and ran at 10-11 ppm 1 ft. below surface. This never varied to much- good news.
From the Trout master, Cecil Barid, I learned earlier in the year that DO levels are more important than temp, but the catch 22 is that when the temps get too high (like 72) the water is unlikely to hold much DO, and they tend to suffocate before getting heat stressed.
