Well, esshup and others are much better at aeration theory than I, but I have read alot and listened to the Pond Boss on this topic.
You can calculate air lift and therefore water lift based on your pond size and diffuser lift ability. You can then do fairly simple math and figure how much water you are moving from bottom to top per 24 hours. It isn't bad to turn the whole pond water over (or around and around) once per 24 hours, but you do not need to move the bottom water to the top multiple time in 24 hours. To figure this out you need some knowledge of the brand diffuser disk, the pore size or rating of the membranes, then how many membranes and what depth they are at.
At 8 feet deep you will move more bottom water in all directions as you don't have as far to go up, you actually go up and out all at the same time.
Your depth, aeration membrane efficiency which means how many bubbles and how tiny those bubbles are will make a big difference in how much 'lift' or water movement you get. If you have really good water movement and the water in the bottom of the pond is turning over to the top more than one time a day then it certainly has a chance to get closer to the surface water temps which is NOT what you want.
Cooler water holds more O2, cooler water helps fish stay less stressed, cooler water is your friend when it comes to slowing down algae growth.
I would say the point of aeration is to make sure that there isn't a completely dead zone of low oxygen water below the thermocline. Getting some oxygen to the bottom also helps the air breathing bacteria do their thing to break down muck. Aeration helps avoid build up of toxic sulfide gas that will lead to a fish kill if that dead, toxic water suddenly flips over due to a big rain event or temp swing.
But you can definitely achieve the positive sides of aeration and still avoid overwarming the bottom zone and super heating the pond. I have never heard that it is the goal of aeration to make all the water homogenous in the pond. Certainly i can think of no advantage to having all the water in the pond the same (homogenous) temperature.
I also can't believe I'm adding wear and tear and higher electric costs by turning the pump on once in 24 hours and turning it off once in 24 hours vs keeping it on all the time. Certainly electric costs are low both ways and I would not figure cost into the equation in your scenario.
Can someone else really into aeration help here?
I think it would still be very helpful to know with 24/7 aeration what your temps are say at 2', 4', 6' and 8' depth. IF you still have good stratification despite 24/7 aeration then you are welcome to do as you are unless you desire the bottom to stay a bit cooler, which in that case, you would purposely aerate only during coolest hours of the day during the hottest months of the year.
