Some years ago, I helped my mother put together a koi pond in her front yard. It's big enough, some 600 gallons, that fish can survive the winter by sinking down to the bottom and waiting out the coldest months in a torpor. The pump keeps the water circulating, and relatively clean. With a few sticks and some occasional netting, she keeps the herons from preying on her fish.
Sounds nice, right? Yeah. Don't get into your swimsuit just yet. Look at this closeup of a stick over the pond where the water splashes.
