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How Do I Know If My Aquarium Heater is Working?

For most fish lovers, there will be a heater in their fish tanks to raise and maintain the temperature of the tanks. But sometimes, the heater is not working, which will threaten the health of the fish. So how do I know if my aquarium heater is working? why it doesn’t work? How to solve this problem? Let’s figure them out.


Why do you need an aquarium heater

Fish are cold-blooded creatures, which means the temperature of their body depends on the temperature of water in the fish tank. Wild fish will swim to different water areas in different seasons. So if you are keeping a fish, you have to adjust the water temperature according to the room temperature.

That’s why you need an aquarium heater. It can keep the aquarium warm for fish who like warm water, such as tropical fish. It can also keep water warm when the room where you put your fish tank is cold.


How to know if the heater is working

There are two methods for you to check--check the light and check the temperature.


Check the light

For most heaters, there will be some indicator lights on them. Different products have different settings, you can read the user manual to see how to check the heater with light. But if your heater has a metal body, you may not be able to see the light.


Check the temperature

You can use 3 different ways to check the temperature.

  • Check it with your hands

Remember to wash your hands before putting them into the fish tank because you might bring bacteria into the water.

Move your hands toward the heater slowly to see if there is a temperature change as you get closer to the heater.

You can only touch the heater when you don’t feel any temperature change since it means the heater might have broken, or your hands might get hurt.

  • Check it with a thermometer

Before you turn on the heater, don’t forget to measure the initial temperature so you can make a comparison to see whether there is a temperature change.

Heating may cost time, so you’d better check the temperature after 24 hours. And you can also use your hands to feel the temperature change because sometimes the thermometer is not accurate.

  • Do a bucket test

It may cost a long time to check if the water in the fish tank has been heated because the capacity of a fish tank is too large. So you can put some water in a small bucket or other containers, then put the heater in the bucket. After waiting for a while, check whether the temperature has been raised or not.


The reasons why the heater does not work

Here are some common reasons why the aquarium heater doesn’t work.


It’s a defective product

When you get a new heater, you’d better test it with a thermometer or your hand. If it doesn’t work, you might have received a defective product. Make sure you have the receipt so you can ask the seller for a new one.


Faulty socket and power supply

An aquarium heater is an electrical appliance. If it isn’t working, check the socket where it plugs in to see whether there is any faulty. You can check it by plugging another appliance in the socket, if the appliance can work, you may have to replace a new aquarium heater.


It is placed improperly

The placement of an aquarium heater is vital for effective heat transmission. If your heater is placed in the wrong place, it will take you more time to raise the temperature. The tank will be partly heated because the water is not circulated properly.

Water is a good medium for heat transfer, so if you put the heater in a proper place, the water can be heated effectively, saving your time and power. To make sure the water in your tank can be heated fully, you can put the heater near circulation points.


It has a badly heatproof

Most of the aquarium heaters are made of glass or materials that can not stand high temperatures. If the room temperature is lowered, the heater may stop operating because the temperature is under a certain level. Without a heatproof, the aquarium heater is easy to break when facing constant temperature change.


Forget to unplug the heater when changing water

It’s a very common mistake. Most people forget to unplug the heater when they change the water in the tank. If the water level is under the heater’s position, the heater will expose to the air and runs dry quickly, then your heater may not work anymore and even give you an electric shock.


It has been overused

Sometimes your heater doesn’t work because you keep it working for a long time. It may need a short break before coming back to work, you can just turn it off and let it have a rest.


The size of the heater is not suitable

For a big fish tank with much water in it, if you buy an undersized heater, you may have put too much load on the heater to raise maintain the temperature. This means the heater may have to overwork to reach the heat that the tank needs, which will cause damage to the heater.


What should you do if the heater is not working

According to the causes, you can deal with the problem in these ways:

  1. For a defective heater, you can ask the seller to change the defective product.
  2. When you are installing and using the heater, follow the manufacturer's recommended installation and usage.
  3. Choose the proper position to make better use of the heater.
  4. If there is some problem with your socket or power supply, change it immediately.
  5. Avoid excessive use by turning it off when the water is heated.
  6. Instead of running a single heater, put two small heaters to share the heating burden.
  7. Clean the heater regularly, make sure there is no algae, salt, or other waste around the heater.
  8. If the heater is broken or has been used for months or years, buy a new one.


    Types of aquarium heaters

    Hanging aquarium heater

    Hanging aquarium heater is the most common heater and the cheapest one. As its name implies, it is hung on the top of the fish tank, usually behind the fish tank, and has a glass tube with a heating element in it. It is put into the tank vertically, which means it can disperse heat to all of the levels.

    But the drawback is that the heat can not be dispersed evenly from one side to the other side. Since the length of the heater is limited, this kind of heater is not suitable for big fish tanks.


    Submersible aquarium heater

    A submersible aquarium heater is fully submerged in the water, which makes it more efficient in heating water. It is widely used by fish lovers because it is easy to install, and it can raise the water temperature in a short time. You can put the submersible aquarium heater at any angle but it’s better to put it horizontally. There are submersible heaters of different sizes in the market, so they are suitable for most aquariums.

    Submersible aquarium heater

    [Check more]

    Aquarium substrate heater

    This kind of heater is the least common one. It consists of a coil or grid of wire, which is buried under the gravel. The wire itself is a heating element. When the heater is on, the wire will be heated and transfer the heat to the gravel in the tank. The gravel will then raise the water temperature.


    Filter aquarium heater

    Some filters may have a built-in heater system. When the water flows through the filter and gets cleaned, it will also be heated by this kind of heater. Then the water goes back into the fish tank will be clean and warm for the fish. It integrates a filtration system and heating system, so you don’t have to leave extra space for a heater.



    We have talked about the importance of an aquarium heater, how to tell the aquarium heater is not working, the reasons why the aquarium heater doesn’t work, what should you do when the aquarium heater doesn’t work and the types of aquarium heaters.

    As human beings, we buy air condition to control the temperature to keep us warm or cool. For your fish, you have to prepare a heater for them. We have given you so much information about aquarium heaters. So next time you find your aquarium heater isn’t working, try to recall what we have mentioned in this article and solve the problem by yourself. It will be an experience accumulation in your fish-keeping life.


    Related Topic:

    Do You Need a Heater in Your Fish Tank
    How to Choose the Right Aquarium Heater

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