With Koi...

As to what happens to the Koi in Minnesota's famously frigid winter they overwinter in the pond. We toss in a couple of pond heaters to keep them nice and toasty over the winter. They go dormant at around 50 degrees (F) and stop eating. The waterfall continues until late December when the ice builds up enough to cause the waterfall to overflow the small stream and then we remove the pump until spring. It's always a great day when the waterfall runs again...

The waterfall is not just for looks or ambiance by the way. The waterfall is also a biological filter to keep the water clear and the waterfall and stream also mix oxygen into the water for the fish to breathe. A pond skimmer (camouflaged in the shore) removes any debris that falls into the pond. Moreover these ponds are great for mosquitoes: If a mosquito lays eggs in the pond any resultant larvae are either eaten by the fish or are run through the filtration system.