As the name of this pond maintenance tool implies, a proper pond deicer is a device used to prevent the accumulation of ice in your pond during the winter months.
In short, Yes! Have you ever experienced a pond developing a layer of ice?
The best way to manage this ice buildup is through the use of a pond deicer.
Specifically, it's used to melt a small hole in the ice which then provides an escape for toxic gases to leave and oxygen to enter the pond.
Pond deicers will prevent winter-kill from occurring altogether.
What size pond deicer you need will solely and largely depend on how many gallons the pond in question holds.
Additionally, there is a factor of using a pond aerator or not to consider.
General Rule is:
Up to 250 gallons: 100 to 250 watt de-icer.
250 to 500 gallons: 300 watt de-icer