5. Perform regular water changes
Cold water holds more CO2, which is acidic. Over time, this depletes the carbonates in your pond water. When they are depleted, a pH crash will likely happen. The water in your pond turns acidic during a pH crash, which is fatal to your Koi collection. It might not be very pleasant to deal with a hose during the winter, but regular water changes will help prevent a pH crash by lowering the overall amount of CO2 in the pond and replenishing the carbonates that buffer the pH.
Keep these tips in mind this winter. The more you prepare, the better your Koi's chances are of making it through winter unscathed.