What about dropping the well water through a packed column, into a pipe and then running the pipe underground close to the bottom of the pond? That way the water is aerated and degassed before it hits the pond, and since it is colder than the water above it in the water column, it should stay on the bottom and not disrupt the thermocline.
I haven't done this in my trout pond but had thought of it. I have dropped the well water through a packed column before adding it to the trout pond, but it was added at the surface. I had enough flow to keep the entire pond no higher than the mid sixties. With the above you may be able to get away with pumping in much less.
