De-icers float in your pond and keep a hole open in the ice, letting bad gases escape out of the pond. These gases – which come from exhaling fish and decomposing debris – would otherwise build up under the ice and suffocate your pond life.
A de-icer will heat up just enough to form a small opening in the ice; it will not cause a significant increase in your pond’s overall temperature. That means your fish will still enter torpor as the temperatures drop, and parts of your pond that aren’t close to the de-icer will still freeze over – which is OK!
Remember: always run an aerator in addition to a de-icer. While you can sometimes run an aerator without a de-icer, we don’t recommend running a de-icer without an aerator.
Another nice feature with de-icers: The ones we use are thermostatically controlled, shutting off when the water warms up. That means you never have to worry about your de-icer wasting electricity.