Do I need a pond heater? That is a common question that I get asked frequently as the winter weather starts to set in. What we first must understand is that the purpose of a pond heater is not to heat the water. Its purpose is to simply keep a hole open in the ice when the pond freezes over. This hole is important for allowing gases to escape from the water, and not build up creating a toxic environment in the water. As organic debris rots in the pond, (leaves, algae, fish waste, sludge build-up, etc), it can give off gasses. The more debris that you have in the pond, and on the bottom, the more the potential for a build up of toxins as well as a higher potential for parasites, bacteria and fungi. As these dirty and stinky environments build up, more problems may arise, and therefore it is important to allow these toxic gases to escape.
Get an air pump first!
What I strongly suggest is to first of all have a good quality air pump with nice air stones in your pond, creating a “boil” of oxygenated water on the surface of the pond. If you turn your pond pumps off for the winter, an oxygen source is very important. See my videos on YouTube on pond aeration and also winter care for more information on that. The air pump will keep a hole open in the ice for most of the winter allowing that gas exchange to occur. Only during the extreme cold will the hole freeze over and a dome of ice will form over it. The air pump however does continue to work under the ice. Only during these extreme cold spells is when I like to use a heater. Having that heater placed near the “boil” from the air stones will quickly reopen that hole and clear the ice from a nice area around it. When the weather warms up, the heater can be unplugged.
The air pump should remain running throughout the winter, but I only use the pond heater when needed. Pond heaters can use a lot of electric to run, much more than most air pumps, and the oxygen is needed all winter, especially if you have large fish or a lot of fish in the pond. Some heaters may have a thermostat, but I find that they do not work as you may think, the water is always cold and therefore it’s on all the time eating a lot of electricity for nothing. So, they are good to have, secondary to a good aeration system, but not needed to be on all winter. A lot of my clients have an air pump running all winter with no heater, and they don’t have any problems. The one point that I would like to make with that however, is that all of my ponds have 4″ bottom drains and gravity fed filter systems….. That means no rock and gravel on the bottom to gather and hold all that rotting debris. My ponds are very clean, so the amount of gasses generated is very low.
Two different types of heaters
There are basically two kinds of heaters that are available. One is like a floating doughnut. It has a very low energy draw, but it will only keep a small hole open in the “center” or “doughnut hole” opening of that doughnut shaped heater. It is ok for smaller ponds with a couple goldfish, but not for larger koi ponds. The second type of heater is much stronger, it is a round disc with a heating coil under it. These heaters are much better, and are often sized as 1000, 1250, or even 1500 watts. The element is exposed on the underside of the unit, and can become hot to the touch. This can be an issue if the heating coil “element” is touching the pond liner or the side of a fiberglass or plastic pond shell for a long period of time. The cold water is often enough to keep the heater from burning a hole through, but it is good practice to set the heater up maybe tied to a string out over the pond so that wind or anything else wont allow it to setup next to the edge of the pond. Some brands do have a “cage” that is sold separately for this purpose, that attaches to the heating coil, and keeps it protected. I don’t find it necessary, if you can just tie it to a string from one side of the pond to the other, and tether it over the pond. Also, if you have your pond covered with netting, you can run the power chord up through the netting in a position out over the pond a bit to also hold it in place. Just remember to keep the heater in close proximity to your aeration.
Do I Need a Pond Heater? Final thoughts…
To conclude, Do I need a pond heater? Well, a pond heater is definitely good to have, but a good aeration system is more important. And you need only to plug in the heater during very cold conditions and not have it running continuously all winter long. One other bit of advice is to never break the ice on top of the pond with a hammer. This can send dangerous shock and sound waves throughout the water. These shock and sound waves can be greatly amplified underwater when your fish are “in a relaxed or dormant” state. For more information check out my videos on YouTube on my channel called Jersey Shore Pondscapes Videos at https://www.youtube.com/channel/UCwW54gcUZItY2EubRDLBNVw You can find the links here on my website: www.pondscapesandmore.com at the top header under YouTube.
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