2.5 acre pond, deepest point is 13 feet.

I have 2 diffusers, one located at 7 feet and one at 5 feet.

My water temps are too high, I'm regularly getting surface temps 90-94 range. This was before aeration.

I'm still on a slow start up schedule for the aerators, currently doing 1 hour per day. Plan to increase to 2 hours per day soon.

Questions:

1. To avoid the water temp climbing higher, should I just leave my aerators at the current shallow depths? I have 2 more diffuser heads I can put in deeper water if I need to.

2. Is there such a thing as too much aeration? My current 2 diffuser system is rated for a 3 acre pond. I have a duplicate setup with another 2 diffuser heads that would be 4 diffusers total which would provide 6 acres of aeration to a 3 acre pond. Would that result in a fish kill or could I still do that as long as I do a slow startup sequence?

3. Several people have mentioned that aerating at night only for high summer water temps. What is everybody's thoughts on that?

4. Assuming that nothing goes wrong, how often do I really need to run the diffuser? Is just a few hours a day enough? Or is there benefit to running 24/7?

I only run my aeration system when the air temp is less than 85 F in the summer time. This means a run mostly at night. My system should, theoretically, turn my pond over several times in a 8 hour period. Rule of thumb is to turn the pond over once per day, but if you are not able to run during the hot daytime...now, you need to turn it over in a shorter run time. My guess is that your 2 diffuser system for a 3 acre pond relies on 24 hour operation...that's a guess. Can you come up with a lift rate for your diffusers and how many gallons your pond holds?

Do not run an aeration system during the hot daytime if you need to keep water temps down. I start to worry when the water 18" below the surface (out away from the bank) gets to be 85 F. BUT you need to feel good about turning the pond over enough. I have read that if the pond has too little aeration (read too little water movement) then you will not get enough turnover to overcome the accumulation of toxic water and all you're doing is making the upper good water worse. I have no proof of that, just read it and it make some sense. Too little aeration is worse than too much unless too much aeration leads to a super-heated pond.

The depth at which your diffusers are located dictates how much water movement you get and that determines how many times the pond gets turned over per day. Do you have a thermocline developing? Probably not just yet as you are in startup mode, but you will want to know that.

My gut tells me that you should get the other two aerators and pump working soon, but I can't say for sure without all the specs on the system and volume and shape of the pond.

Too much aeration will effect water temps if your not careful. Beyond that, turbidity could become an issue, but that is debatable.

Here are couple of my threads where I explore and discuss my aeration system with some calculations and such. I think you will find them a good jump start on your quest...

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Main=37540&Number=489945#Post489945

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Main=38024&Number=494996#Post494996

Keep in mind that I am still learning and experimenting with the whole aeration concept.