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Best Water Heaters For Aquaponics

Best Water Heaters For Aquaponics

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While aquaponics is known to be an environmentally sustainable and efficient method of growing crops, providing adequate care for the fish that supply the vital nutrients to the grow beds is essential to the long-term health of the system. This care includes maintaining good water circulation and aeration, monitoring feed levels, and regulating fish tank temperature. Often, aquaponics practitioners overlook temperature levels in the tank, which can contribute to stress in fish and, ultimately, certain types of diseases. As a result, finding the best water heaters for aquaponics systems may seem like an obvious answer, but not all units will work for every setup.

Before you purchase and install a water heater for your aquaponics system, you should consider the average room temperature of the location in which the tanks will be placed, the total water volume of the tanks, and the desired tank temperature. Keep in mind that different types of water heaters can work well in aquaponics. Here are some of the best varieties to consider:

  1. Submersible heaters
  2. Immersible heaters
  3. In-line heaters

In this article, we will examine why it is essential to have a water heater for your aquaponics setup. We will also discuss some of the best water heaters for aquaponics based on unit sizing guides and other heating functionalities.

Why water heaters are important in aquaponics

Unlike humans, most varieties of fish are poikilothermic or cold-blooded. They do not produce their own body heat, and they rely on the tank’s water temperature for their temperature to be regulated.

According to FAO, the ideal water temperature for aquaponics is between 71° to 84°F (22° to 29°C). Common aquaponics fish such as tilapia, common carp, and catfish thrive more in warm water. Even though they can tolerate temperature dips at night or during storms, using a heater to maintain the water temperature at a steady level and avoid fish stress is ideal. Maintaining a healthy fish population is essential for optimal plant production. Thus, investing in a reliable water heater should be a top priority for aquaponics practitioners.

Fish tank heater size guide

Click to quickly shop water heaters on Amazon

A common mistake of many aquaponics practitioners is buying a water heater without properly sizing the unit. To identify the correct heater size for your system, you will want to note the tank’s total water volume, the average room temperature where your tank is located, and the optimal water temperature range for the fish. Let’s break this down a little further by looking at each of these steps in more detail:

  1. Take note of the total water volume capacity available in tanks. This will be used later when referencing the sizing guide.
  2. Measure the average air temperature of the location in which the tank will be located. Keep in mind; if the unit is outdoors, then the measurement is likely to have a broader range of values due to temperatures differences in daytime, nighttime, seasonality, and geo-location. If the unit is indoors or partially indoors, the average temperature is generally easier to calculate.
  3. Research the ideal water temperature range for the fish you plan to keep. If you keep multiple breeds of fish in the same tank, try to find a healthy balance in temperature between the breeds or only use varieties that have similar temperature requirements.
  4. Lastly, subtract desired water temperature from average room temperature to find the difference. This value is used to help determine the number of Watts needed for your water heating unit.

For illustrative purposes below is an example of this process.

Tank size: 40 gallon

Desired water temperature: 80°F

Average room temperature: 71°F

Calculation of heating required: 80°F – 71°F = 9°F

After calculating the required heater wattage, you can now refer to the size guide developed by The Spruce Pets to determine the correct heater size needed for your tank. For our calculation, which is 9°F, the right heater size for our system would be 100 watts. Typically, if the heating requirement falls between the levels given, choose the larger size.

Tank Size Heater size for

9°F and below

Heater size for

18°F and below

Heater size for

27°F and below

5 gallons 25 watts 50 watts 75 watts
10 gallons 50 watts 75 watts 75 watts
20 gallons 50 watts 75 watts 150 watts
25 gallons 75 watts 100 watts 200 watts
40 gallons 100 watts 150 watts 300 watts
50 gallons 150 watts 200 watts two 200 watts
65 gallons 200 watts 250 watts two 250 watts
75 gallons 250 watts 300 watts two 300 watts

For relatively larger tanks where the room temperature is very far from the target fish tank temperature, buying multiple heaters to achieve the desired temperature is suggested.

Best water heater for aquaponics fish tanks

Water heaters in aquaponics

There are many types of water heaters available in the market, including submersible, immersible, substrate, filter, in-sump, and in-line heaters. Once you have determined the size of the heater your tank requires, you can check out Amazon or other local hardware stores near you to find one that best suits your system. However, if you want the best one for your aquaponics system, the following heaters are highly recommended:

Submersible heaters


Submersible heaters are considered to be very efficient because they’re designed to be placed underwater. This is commonly used for bigger tanks because it provides more consistent heating than hanging or immersible ones.

Usually, submersible heaters are positioned horizontally so the thermostat can read the water temperature accurately. This is essential in turning the heater on and off at the correct time.

Click here to view some of the available submersible heaters from Amazon.

Immersible heaters

Immersible heaters or hanging heaters are made of a glass tube surrounded with a heating element. This heater is placed at the top part of the tank through suction cups or hooks and is not fully submerged into the water.

As compared to submersible heaters, hanging heaters are considered to be less efficient when heating large tanks. Nevertheless, they can provide the right amount of heating for small aquaponics units.

In-line heaters

An alternative method of heating the fish tank for your aquaponics systems is through in-line water heaters. Through this external heating system, you can ensure that the water is evenly heated as it returns to the tank. This is because inline heaters are usually attached to the filtration system.

In-line heaters have a built-in switch, so it automatically turns off when the temperature is reached. If the temperature drops, it will switch on again because of its built-in thermostat.


Water heaters are an integral part of an aquaponics unit because they help maintain a stable temperature for the fish to live. The simple act of heating a fish tank will significantly affect not only the quality of the fish but also positively impact crop growth.

In choosing the best water heater for aquaponics tanks, you should first find out the appropriate heater size for your system. This can be done by performing the calculations mentioned above and referencing a water heater sizing guide. By following these steps, you should be on your way to seeing a happy pool of fish.

The Campbells love finding sustainable and fun ways to increase their independence from traditional brick and motor supermarkets. Aquaponics provides a full lifecycle food source for families and a great hobby. #aquaponicslifestyle

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