De-icing is one of the keys to winter pond maintenance. Invest in a high-qualty de-icer that utilizes at least 1200 watts to ensure there is an ice-free hole in your pond all winter. You'll want to refrain from using the de-icer 24 hours a day for extended periods of time, as draws a lot of energy. It's probably adequate to turn your deicer on for a few hours during the evening or early morning to maintain the hole unless an extreme cold snap is forecast. However, if you are going to be gone for a few days, leaving the de-icer running constantly for this short period of time can help prevent holes from sealing, and keep your fish healthy.
On the other hand, if your temperatures don't usually dip below freezing and you're going to regularly be around your pond and checking on its denizens, then a deicer may not be worth the investment. If you do see a sheet of ice beginning to cover your pond, it's relatively easy to create a hole by pouring hot water over the surface. Don't overdo it on the hot water, though, since sudden temperature changes stress fish and may even cause death.. Finally, whatever you do, never break the ice by force. This will send dangerous vibrations through the water that can seriously harm or even kill your fish.
