First thing, if you get no surface boil from diffuser in deeper water, it is not a diffuser problem but a compressor/pump problem. It is not generating enough pressure to release air at that depth. At 18ft it takes at least 9psi.
Secondly - based on what you've told us so far, I doubt that you will get trout to survive in your pond if surface water temperatures get to 75-76F. Aeration should keep adequate DO as deep as the diffuser is located. Below that depth or maybe 1 ft below that depth there will be no DO soon after surface water is 75-76F. That is the basic thermal mixing properties of water combined with the pond's normal biochemical oxygen demand. Your pond might not be normal or typical. If the surface does not get to 75F then there may be a chance the deeper water will stay cool enough with adequate DO for trout. IMO Mixing with a diffuser cannot usually maintain bottom temps more than a 5F temperature difference and still have adequate DO for trout. As I see it, the best chance of trout survival is to aerate at the fartherest distance from the spring water inflow. Then hope the spring inflow provides enough of a cool water, thermal refuge for the trout.
Second opinions are very welcome. We will find out more on this topic in September when the water cools to below 68F and the trout if alive begin feeding again at the surface.
Last edited by Bill Cody; 05/23/12 09:49 PM.
