To Quickly Create An Opening In Ice For Your Pond, Pour Warm Water On The Surface. Avoid Breaking Through The Ice Using Force Because You Can Harm Pond Life. For pond owners with fish or other inhabitants, winter poses new challenges. While you can move your creatures to a tank inside to wait out the weather, it's just as easy to leave them in their natural space and keep them healthy. Ice itself is not an issue for Koi as long as your pond is deep enough to not become frozen completely. Koi fish and many other inhabitants go dormant in the winter, which means they huddle to the very bottom where the water is warmer and use far less oxygen. The most critical reason why you need to make sure your pond surface doesn't freeze over completely is because it keeps oxygen out and traps toxic gases that can kill your fish. As long as there is a hole, or several, in your pond surface, your fish can ride out the cold weather just fine. You can definitely add a pond ...