Fish Tank Filter Not Working? Here’s How To Fix It

Is your fish tank filter not working? You’re not alone. This is a common problem that almost every fishkeeper faces at some point.

A fish tank filter is an essential part of fishkeeping, and when the pump stops working, it can be a real pain. It hampers the filtration process and can cause the fish to suffer.

An aquarium filter cleans the waste and ensures adequate oxygen in the aquarium water. So, it’s really a nightmare for a fishkeeper if the filter suddenly stops working or does not deliver the expected outcome.

In this blog post, I’ll discuss a few possible reasons why your fish tank filter might not be working and how to fix it without replacing the pump altogether. So read on to learn more!

Fish Tank Filter Not Working: (Most Common 03 Reasons)

Before we discuss how to fix a fish tank filter that’s not working, let’s take a look at some of the most common reasons why this happens.

No Suction In The Pump

One of the most common reasons your fish tank filter pump might not be working is because there is no suction. 

The aquarium filter works through a motor-driven impeller. The impeller creates the suction in the filter housing, and draws the water up through the filter media and back into the aquarium.

If there is no suction, it’s likely because

  • Something is blocking along the line,
  • An airlock in the impeller,
  • The impeller is broken.

When it is plugged in, put a hand over the pump. Is it hot or vibrating? Then, the motor might be ok, and probably there is an airlock or a blockage in the impeller, intake tube, or outflow line.

Reason for no suction in the filter pump

A clogged fish tank filter pump will not be able to deliver the expected outcome, and it will eventually stop working. 

Similarly, if you forget to prime the filter pump, air may be introduced in the filter housing, preventing the pump from creating suction.

Although in modern days, self-priming pumps are equipped with the aquarium filter, some may require manual priming.

Another common reason why your fish tank filter pump is not getting any suction is that the impeller is broken. The impeller is responsible for moving the water through the filter. If the impeller is damaged, the pump may create a grinding noise, can overheat, and obviously no suction.

How to Fix No Suction Problem In The Pump

First, let’s say there is no suction in the pump due to an airlock. In that case, you need to prime the filter pump to start functioning.

If you are using an internal aquarium filter, you need to ensure the pump housing is submerged in the water.

For HOB filters, some are no-prime pumps, and some need to be primed. For no-prime pumps, ensure the adequate water level in the tank for the intake to bring water into the system. For manual priming pumps, pour the water from the top into the filter chamber.

How to Fix Suction Problem

The canister filter sits outside of the aquarium. To prime a self-priming canister filter pump, you just need to push the prime button to bring water into the pump and tubes. Some need to be manually primed, which is done by filling the filter media chamber with water and then placing the lid back on.

Other than the airlock, whatever is the other reason for no suction in the pump, you need to completely disassemble the filter. First, unplug the filter, and follow the manufacturer’s guidelines to take it apart.

Search for the clog, flush out the chamber with tank water for the media (to preserve beneficial bacteria), and clean water for the impeller. In addition, make sure it spins in the chamber before reassembling and returning to the tank.

If your fish tank filter pump is not working because the impeller is broken, you’ll need to replace the pump or the filter altogether. 

Filter Stopped Functioning Entirely

If the pump is cool to the touch and without any vibration when plugged in, the issue is probably related to the motor or power source.

Filters for fish tanks sometimes don’t run, remain silent, or simply won’t turn on for various reasons. 

The most common reason why your fish tank filter pump stopped working are:

  • Faulty power source
  • Clogged motor
  • Motor burn out

A potential problem for the pump to stop functioning entirely is the power source or the connecting cables. For example, there may be a blown fuse, a tripped breaker, a broken wire, or a tripped circuit breaker. Also, if you use an extension cord, a small voltage drop can keep the pump from working.

The reasons for filter not working at all

A clogged motor is another cause. Sometimes dirt and debris can accumulate inside the motor itself. It can hamper the motor rotation, cause the motor to overheat, and eventually burn out. Some motors may have built-in overheat protection to prevent burnout.

Motor burnout can happen for other reasons, like a power surge in your home. A power surge may occur due to lightning strikes, short circuits, power outages, etc.

It can cause the filter pump to stop functioning and may require waiting for a few hours before turning it on. However, a power surge can also completely burn out the motor coil.

How to Fix a Fish Tank Filter Pump That’s Not Working

If your fish tank filter pump stopped working entirely, don’t despair. With a bit of troubleshooting, you should be able to figure out the problem and get your filter up and running again. As you now know the common reasons, there are a few solutions you can try.

First and foremost, check the plug for power to ensure it hasn’t come loose. It is incredible how often this happens and how few people check it.

After that, check the power source, the power cord, the extension cord (if any), the outlet, and the circuit breaker. 

The fix for filter not working at all

Try plugging it into a different outlet or using a different extension cord. It’s better to connect the filter directly to the socket than an extension cord.

If the motor is clogged, you can try to disassemble it and clean it with a soft brush. Make sure to unplug it from the power source before doing so. You can clean the motor with clean water if it’s waterproof.

For a burnout motor, you’ll need to replace it. You can buy a new motor or a new filter. If you decide to buy a new filter, make sure the pump size is appropriate for your fish tank.

Read the complete review on the best aquarium filter if you want to buy a new aquarium filter.

#03: Improper Flow Rate

Improper flow rate is another common issue that fishkeepers face with their fish tank filter. This is usually caused by the wrong size of pump for the fish tank or by the wrong size of tubing.

If the flow rate is too low, it can cause problems with the fish and the filtration system. The fish will not get enough oxygen, and the filter won’t be able to remove the waste. This can lead to fish death, a dirty fish tank, and algae growth.

Reason for Improper Flow Rate

If the flow rate is too high, it can cause the fish to be stressed and can also damage the fish’s fins. It can also move too much water and create an overflow.

How to Fix Improper Flow Rate in a Fish Tank Filter

There are varied preferences for water flow among aquarium fish. For example, some species from lakes or ponds prefer slow-moving waters while others living in mountain streams and rivers would like faster currents.

Before buying an aquarium filter, try to figure out the types of fish you want to keep in your aquarium; select the filter size based on that. Also, don’t forget to measure the fish tank to get the right size pump.

Fix for Improper Flow Rate

If you are unsure, and your mind may change afterward on fish preference, in that case, the best way to fix it is to get a fish tank filter with adjustable flow. You will be able to adjust the filter intake flow (output as well) by simply sliding a lever.

Suppose your filter is not adjustable, and the flow rate is too high. Then, you can manually try to reduce water flow in two ways:

  • Creating some restrictions inside the filter intake. For example, use foam or clothing to slow down the rate of water coming into the filter.
  • You can also disperse the outlet flow by making a baffle arrangement or using a spray bar. Baffle can be anything strong enough to redirect the flow. It could be a mesh screen, plastic cups, or bottles.

However, if your aquarium filter is too low, there is no other way but to supplement the filtration.

Frequently Asked Question (FAQs) On Fish Tank Filter Not Working?

Why Does The Fish Tank Filter Not Working After Cleaning?

There could be a couple of reasons. First, make sure you assemble it right after the cleaning as per the manufacturer’s guidelines. Don’t forget to turn the flow valves in the open position if you use the canister filter.

Another reason is probably an airlock. You need to prime the filter properly to begin water circulation. Check the water level for internal submersible and HOB filters. Follow the below video for the canister filter to remove the airlock.

Fish tank filter not working will fish die?

It depends on how well you control the damage. Filter circulates water, removes toxins, and provides necessary oxygen for your fish and beneficial bacteria. 

So, if the filter stops working, all the processes will be hampered. Toxins will start to escalate, and you need to keep that in check.

You can perform a 25% water change daily for the interim period and deploy an air pump to provide necessary oxygen. Chances of fish survival rate will depend on the waste accumulation rate. Try to fix your filter as soon as possible or buy a replacement.

Generally, fish may survive a minimum of 3-5 days and a maximum of 7-15 days without an effective filtration unit.

The fish tank pump is not working after a power outage.

The most common reason is priming. If your filter pump is not a self-priming one, you need to manually prime the pump every time you want to start it. For example, you have to prime it when a pump stops during a power outage. It won’t be required for a self-priming pump.


A fish tank filter pump not working can be a big problem and can cause fish death. Unfortunately, there are many reasons why the pump might not be working, but fortunately, there are also many solutions.

Be sure to check the manufacturer’s guidelines for your specific fish tank filter model. If all else fails, you can always buy a new pump. Thanks for reading! I hope this was helpful.

If you have any questions or comments, please feel free to leave them below. I always love hearing from you!

Sujit Modak

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