birddog and bruce,
For birddog's scenario of keeping trout, the surface agitator is a better option than the diffuser. The cooler water will retain more oxygen yet your thermocline will not be disrupted in this small pond. The hole created will allow the sun to enter the water column while the lake will off-gas the carbon dioxide and hydrogen sulfide build up. And for summer, the surface aerator is a better option for a trout pond since it will not disrupt the thermocline at that time of year either. The trout will be able to keep in the lower cooler waters during the summer.
Now if the lake was larger, we could work with a diffuser and not totally disrupt the thermocline.
Birddog, since you are in MN, the company that Bruce is speaking of is located in your state. KascoMarine.com Talk with Bob Robinson.
Good Luck!
