I have a concrete pond I built with block, 22 feet long, 14 wide, 2.5 deep. Its in almost full shade with a small stream that can be allowed to feed it (or not if water is too warm) PLUS, a well that is on a timer for 1 hour on, then 1 hour off....well water is 52 degrees and in Pennsylvania in the summer, the pond definitely gets to the mid-60's....at that point the fishes survival is touch and go....if ther is a power outage, the fish are dead in 20 minutes as the oxygenating pump is done and so is the cold water supply......I have had many fish kills over thew past 15 years........trout are very hard to keep especially in unnatural conditions........the plus side is they are cheap, and restocking with 12-inchers is only about 3 buicks apiece....