Is A Pond Heater Necessary?

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Written By Mark Washburn

Mark has 20 years of experience as a professional pond management consultant.

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A good and timely question from Esther who asked, “I have a small pond in my front yard I have 2 koi and 3 goldfish, I live in South Carolina and in the winter the temperatures can drop down to freezing but they recovered with the sun. I don’t think the pond will freeze solid but I’m wondering about my fish. Should I put a heater in the pond? What temperature should I try to maintain the water? “

Thanks for the question Esther!

Here’s my take on your situation.  I think you will probably be just fine without adding a heater to the pond.   You live in a warm enough climate that the pond shouldn’t freeze up very much or for very long. So as long as the pond isn’t ice-covered and locked in for a good period of time the fish will stay safe.

Many people think a pond might need to be heated for fish so they can stay comfortable but that’s not really why the device would be used

I should also clarify that the term “heater” isn’t quite accurate when it comes to the most commonly used wintering tools for small ponds.

As you look around online, you will end up finding a lot of options when it comes to pond deicers, but not many pond heaters.  For most pond owners, simply keeping a pond free of complete ice coverage on the surface, or even just maintaining an opening in the ice, is enough to keep fish safe throughout the winter.

Maintaining an opening in the ice allows fresh oxygen to come into the pond and any unwanted gases to flow out.  Since most deicers have built-in thermostats, they only come on when the ice-up starts and will turn off once things warm up again.

I’ll often remind people too, that you should cut back on feeding your fish as the weather cools off and once the water temperatures get below 50 degrees it’s fine to stop feeding altogether.  Fish will typically slow down quite a bit as things cool off and that includes their metabolism and digestive system.  So let the water temperature and your fish’s activity level dictate when and when not to feed during the winter months.

Some people also may use a small aerator or bubbler to maintain an opening in the ice.  I have no issue with this approach as it helps circulate the water a bit, but oxygen, or more precisely, low oxygen, isn’t as much of an issue in the winter months as cold water will retain a lot of oxygen compared to warm water.  If you do use an aerator, I would generally move them towards an edge of the pond and not at maximum depth.  Again your only real goal with this is just to keep a spot of ice open for air and gas exchange.

Anyway, getting back to your question on the pond heater or deicer…for those folks that live in consistently cold winter climates, here are a couple of models that have been proven to work well for people over the years.  Most of these are true deicers but for people with very small ponds like yourself, they may be better served with an aquarium heater.

Simply choose the one (based on wattage) that is best rated for your pond’s gallon volume.

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