I have wondered about running a heat exchanger loop like a heat pump would have to cool a small pond. Taking in the warm top water and pumping it into the loop and then just back into the pond. If the loop is long enough and in the 53* ground you could keep the water temp year round.
One would have to calculate the thermal loss of the surface area of the pond. It would be like creating your own cold water spring.
Cheers Don.
The downside is you would not be dilluting mebabolic waste products and flushing them out as you do with the infusion of freshwater with flow through. Trout are very sensitive to ammonia and nitrites and even nitrates, which could become an issue at some point depending on the density of the trout.
