Pond Heater Guide: What is the Best Pond Heater?


As winter approaches, it probably means you are thinking about your fish pond and how to keep it at an adequate temperature until next spring. When it comes to heating a pond, it may seem complicated because there are many available options. In addition, you need to consider many variables such as the size of the pond, how many degrees you need to increase, type of fish you keep, and more.

Why You Should Heat Your Pond

First, let’s consider why you should heat your pond. Heating your pond is important because it protects your fish from cold temperatures that could harm or kill them. However, depending on your setup and the type of fish you keep, heating the entire pond may not be necessary either. Therefore, it’s important to consider all available heating options.

Another reason to keep your pond heated, or at least above freezing temperatures, is to prevent your pond equipment from getting damaged. If the entire pond freezes, your pump and UV filters can be damaged severely.

There are four types of pond heaters that are popularly used. They are gas-fired boilers, electric inline water heaters, solar heaters, and de-icers.

Pond Heater

What is the Best Pond Heater?

For most pond owners, the best pond heating solution is a pond de-icer. Pond de-icers are the best option for the vast majority of pond owners due to its cost efficiency. Heating an entire pond to a specific range of temperature all winter can be very expensive. In most cases, such expensive solutions are not necessary. If your goal is to simply keep your koi fish alive and healthy during the winter season, the de-icer will solve the most critical issues. Of course, extreme temperatures may require other heating solutions. However, at such extreme temperatures, bringing the fish to an indoor pond or tank may be a better solution.

The purpose of the pond de-icer is to prevent a small area from getting frozen, which will allow proper gas exchange. It will allow the oxygen to come into the water, and release the toxic gas from building up in the pond. In order to assist with this gas exchange, add an aerator. However, do not install the aerator too deep. If you install the aerator too deep, it may unnecessarily agitate the warm water that remain in the lower portion of the water.

If you are not heating the entire pond, make sure your pond is deep enough for your koi fish. It should have a depth of at least 4 feet.

In addition, be sure to adjust the feeding schedule for your koi fish. When the temperature drops, so will their metabolism. It should not be fed the same amount or type of food as the summer seasons.

Different Types of Pond Heaters

While we’ve established that pond de-icers are the best option for most pond owners, let’s further understand the different options of pond heaters that we have. Starting with pond de-icers, heating solutions for ponds include in-line pond heaters and gas boilers.

Pond De-Icer

Pond de-icers are used to keep a hole open in the ice, when the pond freezes over. Without a de-icer, the gas exchange will not occur in the pond. This will cause low oxygen levels and a build-up of harmful gas inside the pond. By keeping a hole open on the surface of the pond, it will allow proper gas exchange and maintain a safe environment for the fish.

Keep in mind that the de-icer is not designed to raise the temperature of the entire pond. Instead, it is designed to produce heat in a concentrated area and prevent that specific area from getting frozen. If the pond is large, multiple units can be installed to achieve the necessary amount of gas exchange.

Many fish, including koi fish, are able to survive low temperatures. As long as there is proper gas exchange at the surface of the water, the temperature of the entire pond may not have to be raised. This is one of the cost effective ways to keep your pond habitable for your koi over the winter. However, it can still be expensive to run the de-icer all winter for your pond.

Here’s a tip a few tips on saving costs when operating the de-icer.

Install a Thermostatically Controlled Outlet

This will allow the de-icer to run only when necessary. For example, a good setting will be to run the de-icer only when the air temperature is below 35 degrees Fahrenheit.

Install an Aeration Kit

An aeration kit will allow more efficient gas exchange by circulating the water in the pond. The bubbles formed by the aeration kit in itself can prevent some ice from forming as well. In addition, the aeration is beneficial for maintaining cleaner water, healthier plants, and healthier fish.

When installing a pond de-icer on a pond that is already frozen, do not break the ice. This could shock the fish inside the pond. Instead of cracking the ice with force, carefully pour hot water over it. Create an opening that is big enough for the pond de-icer to fit. Once installed, the unit will do the job.

In-line Pond Heater

In-line pond heaters are reliable heating solutions that are designed to slowly heat the water as it passes through a heating chamber. These units are compact and easy to maintain.

The general rule of thumb for the heating capacity for in-line pond heaters is to have 1 kW per 1000 gallons of water. There are variables that could influence this general guideline. For example, if the air temperature is drastically lower than the desired temperature, more power may be required.

Another factor to consider is insulation. If your pond is well-insulated, a moderately powered heater may be sufficient. Since heat rise to the top, one of the best ways to reduce heat from escaping the pond is to place a cover over the pond. A heavy duty plastic covering can be very effective. However, even a simple netting cover can reduce the wind drag, which will make a difference in the amount of heat loss.

Keep in mind that heating your pond all winter can be expensive, even with insulation. Heating a 1000 gallon pond with a 1 kW heater can easily cost well over a $100 USD a month to run. Of course, these are estimates, and it can vary widely depending on various factors.

Gas Boiler

A gas boiler is a powerful solution for heating your pond. It heats water within the heating system, which is used to transfer the heat to the pond water. It doesn’t actually boil the pond water directly, but it uses multiple chambers within the heating system to exchange to the heat to the pond water.

While gas boilers have the capacity to heat large ponds, they are expensive. In addition, maintenance of these units may require a professional, which will add to the cost as well. In fact, these gas boilers are often used for heating swimming pools.

Fish Laboratory

With decades of collective fishkeeping experience, we are happy to share the fish care tips that we've picked up along the way. Our goal at Fish Laboratory is to keep publishing accurate content to help fishkeepers keep their fish and aquarium healthy.

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