Reasons My Top Fin Heater Not Working (Solutions Included)

An aquarium heater is one of the essential parts, especially in the winter season. It keeps the temperature in the tank stable. So, it is important to check regularly if it is operating well-handed.

But what to do if the top fin heater not working? What are the reasons behind it?

Well, in many cases, where one of the parts of the heater or several parts get broken, there is nothing much to do. You have to replace the heater and get a new one.

However, the main reasons of a broken heater are power socket damage, thermostat damage and heater not plugged out during cleaning.

However, some of the problems can be solved and I will talk about that later in this article.

What Happens When Aquarium Heater Does Not Work?

Certain kind of fish needs a certain temperature to live. Such as tropical fish cannot live in cold water. The aquarium heater maintains the temperature in it as needed. A broken heater means a digester in water temperature.

If your fish need a certain temperature, maybe that is cold or warm, an aquarium heater can maintain that. It helps the fish to thrive in the water and many cases, breed well.

Uneven water temperature for a long time can kill your fish. So, you need to check the water temperature regularly.

How to Know If Your Heater is Broken?

If you are completely new as an aquarist, there are several indications you can check to know if your top fin heater working or not.

Check the Indicator Light

If your heater is working properly, the light should be on. So, by simply checking it you can initially know if it’s working or not.

Some of the heaters come with a metal body. In that case, you will not be able to see the light. Fortunately, the top fin has an indicator light, especially for this purpose.

Check the Temperature

If you still have confusion after checking the light, the next thing to do is to check the temperature. You can use a thermometer or your hand. Make sure to wash your hand before putting them into the water.

I prefer to check the temperature by hand because a thermometer can be confusing as well. To check the heater, slowly put your hand into the water directed to the heater.

If the heater is working you will feel the heat emitting heat and the water is getting warmer around it. But if it is not working, there will not be any heat, even when you touch the heater.

Increase the Temperature

Sometimes the temperature of the weather can drop and make the water cooler than usual. You can check it by increasing the temperature.

Increase the temperature 4-5 degree higher and wait for some time to see if there is any change in the water.

If not, maybe it is not the weather.

Reasons My Top Fin Heater Not Working and How to Solve It

As promised, I am talking about some reasons why maybe your top fin heater not working. If there is a way to fix it, I will mention it as well. So read on to know.

Burnt Heater

Sometimes the heater gets burnt when you are not careful enough while maintaining it. An aquarium heater is supposed to heat the water.

So, whenever the heater is on outside the water, it gets burnt and stops working.

The Fix

Once it has burnt you have to replace it.

What you can do is always unplug the heater before you do any kind of maintenance work. It is safe for both you and the heater.

Broken Heater

The top fin aquarium heater is made of Shatter-resistant quartz glass. If you are using it for a long time, the glass can break during its usage.

It can also happen if you are not careful enough while transferring the water or while cleaning. Or if you have overstocked the tank with decorative objects.

If this happens you can easily see that. Or you can also take the heater out of the water and check if there is any breakage.

The Fix

When the heater is broken there is nothing much to do. It is better to get a new one.

If you still want to check if it can be repaired or not try to call a professional for it. I do not recommend it to do it yourself at home.

You can use a heater guard to prevent further damage.

Damaged Heating Coils

A heating coil is a part of the aquarium heater. When the coils get damaged the heater stopped working.

It can get damaged due to long time use. Plant and algae can grow molds inside the coil and damage it.

When this happens, either the heater stops working or overheats the tank. Which can stress out the fish. 

The Fix

Replacing the coils is the best solution in this case. You can do it at home easily.

Try to buy nichrome heating coils as it has high resistance to heat.

Undersize Heater

There is a general rule for the power of the heater you should use according to the tank you have.

If you have an aquarium 50 gallons or smaller, you are going to need 5 watts per gallon and 3 watts per gallon if your tank is bigger than 60 gallons.

If your heater is lesser-powered than needed it will get damaged very quickly. That is because, it will have to run all the time yet, not be able to produce enough heat or vice versa.

The Fix

The solution to this problem is to maintain the rule according to the size of your tank.

Another thing you can do is, use multiple heaters in lesser watts. So, they can work together as a whole and provide the necessary heat.

Salt Creep and Minerals Build Up

After some time working inside the water, salt and minerals build up on the body and parts of the submergible heater like the top fin.

Eventually, it interrupts the efficiency of the heater. In extreme cases, the heater stops working.

The Fix

Cleaning salt creeps are not easy. To clean it, take any detergent and make s solution for it. Dip the sponge into the solution and gently rub the affected areas.

Use a small brush or vacuum to clean the inside as much as possible. Maintain a regular cleaning schedule to prevent build-ups.–nss


Top Fin aquarium heaters are well known for their service. But everything has its own limits. The reason can be any one of the above for a heater not working.

To be honest, the lifespan of an electronic device is uncertain. So, I cannot tell you how long a top fin heater will work or stop working. But well maintenance can prolong the time.

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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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