If you have fish in your water garden, always check your pond throughout the winter months. Your fish’s metabolism will slow down and they will go to the bottom of the pond. To provide oxygen during the freezing temperatures you need to keep a hole in the ice to release the build-up of toxins. Having an aeration system or heater running will help keep the hole open unless we experience exceptionally cold temps for an extended period of time. In which case, you will need to break up the ice manually.