How to Troubleshoot a Marineland Heater that is Not Working?

What if your Marineland heater one day refuses to turn on or fails to warm the water? Even with the most modern Marineland fish tank heaters, this might happen at any time.

But, why does a heater develop a fault? How can you fix a heater that refuses to work?

You should check the connections above the coil while troubleshooting the Marineland heater. If the terminal has been detached from the coil, reattach it. Additionally, you have to fix the damaged coil and clean the contacts.

Continue reading this article to learn more about these troubleshooting techniques.

What Causes the Problem? 

One reason with a faulty Marineland heater is a loose terminal. Many people face this problem with their Marineland fish tank heaters.

Additionally, the heater’s connections may corrode. The effect will be an obstruction in the flow of power. A damaged coil is another cause of a Marineland heater failure. The damaged coil can be examined physically or visually.

You can restore the damaged heater if you can resolve the problems on your own.

4 Steps to Troubleshoot a Marineland Heater Not Working: 

Your Marineland heater may break down if you find that the water in the fish tank isn’t becoming warm. Users of Marineland heaters frequently have this issue, but they are unsure of how to fix it.

However, when the Marineland aquarium heater breaks down, consumers frequently replace it. But if you know some really simple troubleshooting techniques, you can solve it.

I’ve compiled the Marineland fish tank heater fixes that are the most effective. To fix your heater effectively, follow this detailed and step-by-step guide.

Things required to troubleshoot the Marineland heater not working:

Here are some tools and materials that you might need for troubleshooting a Marineland heater not working:

ScrewdriverSoldering tool (if needed)
Protective glovesSoldering coil (if needed)
TorchSoldering mat (if needed)
BrushRust remover (if needed)
Sharp toolThermostat (if needed)

Step 1 – Inspect the Terminals:

First of all, plug in the heater in the outlet and inspect the indicator light. In this case, the indicator light is not illuminating.

Now, open up the heater by using a screwdriver. Take the glass tube off of the heater.

After that, take out the coil. Now, look at the terminals of the fish tank heater coil.

The terminals might become loose. You have to attach them with the coil if they are not connected properly.

Step 2 – Attaching the Loose Terminal:

Use a small sharp tool to release the end of the coil.

 release the end of the coil.

Now, take it out of the terminal end of the coil formation.

Now, solder it properly and make sure it is strongly attached to the terminal.

it is strongly attached to the terminal

Use soldering coil if necessary.

Use soldering coil if necessary
Use soldering coil if necessary

Finally, put everything back in order by reassembling the Marineland heater. Now, the indicator light should light up and the heater will work normally.

Step 3 – Cleaning the Contacts:

Open up the Marineland heater the same way and reveal the connections. You might see some orange or red colored corrosion on the connections.

 orange or red colored corrosion on the connections.
orange or red colored corrosion

The corrosion can break off the connection or prevent current flow. You have to clean the area and get rid of the corrosion.

You have to clean the area and get rid of the corrosion.
clean the area

Apply rust remover on top of the corroded metal. Now, clean the area thoroughly with a small brush.

 the area thoroughly with a small brush

After cleaning the rust off, reassemble and test out the heater.

test out the heater.
test out the heater.

Step 4 – Repairing the Broken Coil:

The coil of the Marineland heater might also break from the middle. As a result, the connection won’t be complete with both of the terminals. For this reason, the heater won’t heat up.

First of all, take the coil out by following step 1 of this tutorial.

the Broken Coil
the Broken Coil

Now, thoroughly inspect the coil for any kind of indication of wear and tear.

 wear and tear.
wear and tear.

To fix this problem, you can use a set of pliers to connect the broken-off coil by twisting both ends together.

To fix this problem,

To make the connection permanent, solder the coils together. Now, test the heater by connecting it to the outlet.


  1. Be careful while taking the glass tube off from the submersible Marineland heater as it can break due to contact.
  2. Use a set of protective gloves while soldering the terminals and the coils together.
  3. While cleaning off the corrosion from the connections, do not put too much pressure on the terminals as they can become detached.
  4. Turn off the power and take out the plug from the outlet before working on the Marineland heater. Also, let it cool for 30 to 60 minutes in the water before taking it out.
  5. Always make a drip loop with the Marineland heater power cord to prevent water from entering the power outlet.
  6. Never turn on the heater outside of the water while testing it after troubleshooting procedures.

Frequently Asked Questions: Marineland Heater Not Working

What type of Marineland heaters are available in the market?

Currently, you can buy only Precision Submersible Heaters from Marineland. The powers available are 50 watts, 75 watts, 100 watts, 150 watts, 200 watts, 250 watts, 300 watts, and 400 watts.

Are the Marineland fish tank heaters safe?

The United Pet Group has recalled around 1.2 million Marineland heaters in 2011. These were the Marineland Stealth and Marineland Stealth Pro models. Since then, the heaters have become safer from fire and cutting hazards.

What special features are provided with the Marineland fish tank heaters?

The thermal switch of the Marineland heater automatically shuts down if the temperature goes beyond a set temperature. Also, the mesh heating component is enclosed around the mica core for better heating.

Should I install multiple Marineland fish tank heaters inside the water?

If the fish tank is large, you might need a powerful heater to heat the water efficiently. But sometimes, one heater is not enough to raise the temperature of 200 to 300-liter fish tanks.

Usually, the power of the heater should be twice the volume of water in liters. So, you would need two 200-watt powered Marineland heaters to raise the temperature of the water of a 200-liter fish tank.

What happens if I do not use a fish tank heater?

If you live in a hot climate, you might not need a fish tank heater in the summer. But you should install one in the winter. Otherwise, the preferred temperature of various fish species can’t be maintained.

What is the ideal temperature in a fish tank?

You should keep the temperature level at 24 to 27 degrees Celsius for tropical fish, shrimps, African and South American cichlid, brackish water fish, saltwater fish, and reef tank fishes.

For pond fishes, the temperature should be kept from 0 to 30 degrees Celsius depending on the fish. For axolotls and turtles, keep it between 16 to 18 and 22 to 26 respectively.

Final Verdict

A fish tank heater is a vital element for the fish to thrive. If the temperature is not suitable for the fish, it may soon die of cold. So, if your Marineland heater stops working, you should look for a solution quickly.

I have included 4 steps on how to troubleshoot a Marineland fish tank heater. Follow my instructions thoroughly to fix these most common issues people face with this specific brand.

Also, be sure to follow the tips and use the suggested tools and materials as necessary.

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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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