How to Troubleshoot an Aqueon Heater that not Working?

Due to the fact that some species need specific temperatures to survive, the fixed temperature might be a serious issue. But, why is the aquarium heater not functioning, and how may the problem be resolved?

Start by checking the heater’s glass for any cracks. Then, swap out the old or broken thermostat. Install an external thermostat as well. Be sure to examine and troubleshoot the knob and indicator light. Use a heater whose power is appropriate for the capacity of the aquarium.

So, if you want to know the troubleshooting techniques for an Aqueon Heater not working, read on.

What Causes the Problem? 

If you have an Aqueon aquarium heater and your aquarium’s water isn’t warming up, your heater may be broken. However, a heater for aquariums may be impacted by a variety of problems.

Your heater may have cracked, your aquarium may be too large for your heater’s power, or your heater may have broken down.

Other problems, such as a broken thermostat, an incorrectly adjusted thermostat, uninsulated glass, and others, might make the Aqueon heater malfunction.

Also, if the power of the heater is low compared to the tank, you might speculate that the heater is not working.

4 Steps to Troubleshoot an Aqueon Heater not Working: 

This is a common problem whether you install a new heater or use an old heater for your aquarium. Many Aqueon owners who have this issue often purchase a new heater for their aquarium.

But that isn’t the ideal or most worthwhile answer. There are a few standard techniques of troubleshooting that may help you save a lot of money. If an Aqueon heater breaks down, not every one of them needs to be replaced.

I’ll walk you through the troubleshooting procedures in this post.

Things required to troubleshoot the Aqueon heater not working:

Take a look at the list of equipment and supplies needed for the troubleshooting activities:

Nonconductive safety gloves
External thermostat

Step 1 – Look for Cracked Heater:

If you notice that the heater is cracked, you can repair it yourself. Disconnect the plug cover at the heater’s base. The thermostat should then be removed from the glass.

 then be removed from the glass.
the glass.

Then, inspect and ensure that all of the connections are operational. Use strong glue to repair the broken heater glass. You should also take care to apply the adhesive gently.

the broken heater glass.
the broken heater glass.

Additionally, rotate the tube and apply it to every part of the cracks to keep water out.

Step 2 – Faulty or Old Thermostat:

If the thermostat provided with the Aqueon heater has become faulty, it won’t work properly. As a result, you will not get a proper reading from the thermostat.

Also, if the thermostat gets old, you should replace it since it loses its accuracy to give the correct reading.


Installing an external thermostat is the best idea for a replacement thermostat.

Inspect and set the heater setting according to the temperature on your aquarium thermometer. Also. Do not abruptly adjust the water temperature in your Aqueon aquarium.

Step 3 – Indicator Light Not Illuminated:

The indicator light might not be working with your Aqueon heater. If the light is off, you should rotate the temperature control knob on top of the heater.


The mini heater and flat heaters from the Aqueon do not include any indicator light. But the submerged heater has a built-in indicator light.

The mini heater
The mini heater

The indicator lamp light lights up when the set temperature is above the water temperature. So, if the light is turned off, you should turn the dial.

If this still does not work, you have to make sure that the connection of the knob is attached properly.

Step 4 – Low Powered Heater:

If you are using a heater with low power, it may be unable to heat the water inside the aquarium. The required heat may be more than that produced by the Aqueon heater.

The required power of an aquarium heater depends on the amount of water inside the aquarium. If you want to increase the temperature of your 200-liter aquarium by 15 degrees Celsius, you will need two 200-watt Aqueon aquarium heaters.

Powered Heater
Powered Heater

Here is a chart to determine how much power you need according to the volume of your aquarium:

Volume of Water Power for increasing the temperature 15 degrees Celsius
20 Liter 75 Watts
40 Liter 75 Watts
75 Liter 150 Watts
100 Liter 200 Watts
150 Liter 300 Watts
200 Liter Two 200 Watts
250 Liter Two 250 Watts
300 Liter Two 300 Watts


  1. Disconnect the power plug from the outlet before changing the water or putting your hands inside the water.

2. Do not let the water level drop below the submersible Aqueon aquarium water heater.

3. Do not let the water go inside the outlet by creating a drip loop.

4. If the plug or the outlet gets in touch with water, do not unplug the cord. Instead, cut off the power by disconnecting the circuit breaker.

5. Do not take the heater out of the water before letting it rest inside for at least 30 minutes after turning it off.

6. Do not turn the Aqueon heater on before 30 minutes after putting it inside the water.

Frequently Asked Questions (FAQs)

What should I do if the Aqueon heater does not raise the temperature after 24 hours?

Check the temperature using a thermometer and unplug the heater. Ensure that the water level is above the heater. Also, ensure adequate water circulation.

How do I install an Aqueon aquarium heater?

First of all, attach the suction cups provided with the package. Avoid installing the cups over the heating portion of the Aqueon heater.

 aquarium heater
aquarium heater

Now, install the heater inside the water in a vertical position or horizontal position. But Aqueon suggests placing their submersible heaters vertically inside the aquarium.

horizontal position.
horizontal position.

Lastly, after 30 minutes, plug the heater and turn it on.

How does an Aqueon heater get cracked?

The outside glass of the Aqueon heater break if collided with the pebbles inside the aquarium. Also, big fishes may bump into the heater and develop cracks.

Why is smoke coming out of my Aqueon aquarium heater?

The main reason is a cracked heater. Other common reasons are an old heater, sudden power surge, set to high temperature, forgetting to turn off the heater before taking it out of the water or changing the water.

Why is my Aqueon heater light flickering?

The main reasons for the indicator light flickering are a broken thermostat, improper supply of power, and heater malfunction.

Other possible reasons are current flow through the filter and fast and unusual patterns of heating.

Which type of Aqueon aquarium heater is best for home aquariums?

The best option is the Submersible Glass Heater. Other options available from Aqueon are Pro Adjustable Heaters, Aquatic Flat Heaters, Mini Heaters, and Preset Heaters.

How do I temporarily maintain the temperature of the aquarium without a heater?

You can use towels, blankets, or heating mats to wrap up small aquariums. Also, a powerful light along with a hood can keep the temperature stable. Proper insulation and placement of the aquarium also affect the temperature.

Final Verdict

Sometimes, many users of the Aqueon heaters face malfunctioning heaters. After installing the heater properly or after using it for several months, it may fail to heat the water.

There are several reasons for this issue. I have discussed all of these issues and provided the troubleshooting techniques.

Follow all of my instructions properly and use the mentioned tools and equipment for the best solution. Remember that you have to take fast action to save the fish from dying in cold water.

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Arif H Fahim

Welcome to PetFishTank! My name is Arif. I make an effort to publish educational articles using my many years of expertise as a fish owner.

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