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Aquarium Filter Not Working: Common Reasons and How to Fix Them

Fish tank filters are one of the most important equipment you’ll need as an aquarist, offering helpful benefits to both you and your fish.

An aquarium filter not only makes cleaning and maintaining your tank much easier, but it also adds aeration and breaks down waste to keep your fish healthy and happy.

However, fish tank filters can break or seemingly stop working, which can be stressful and frustrating, especially if you’re not sure of the cause.

Finding the problem

If you’re currently dealing with a temperamental or non-functional fish tank filter, you’re in the right place! I’ll be going over the most common problems why aquarium filters suddenly are not working and what you can do to fix them.

Importance of a Fish Tank Filter

Without a fish tank filter, your aquarium will quickly become dirty, cloudy, and polluted…

Proper filtration is key in a fish tank as it helps break down fish waste, leftover food, and toxins like ammonia and nitrite by providing a place for beneficial bacteria to grow.

Without a fish tank filter, your aquarium will quickly become dirty, cloudy, and polluted.

This not only looks unsightly, but also puts your fish’s health at risk.

A good-quality filtration system also aerates the water so your fish can breathe.

How Long Can Fish Survive Without a Filter?

The length of time a fish can survive without a filter greatly depends on their health, the cleanliness of the water, and whether there are any other sources of aeration and filtration in the tank.

In an unclean environment without aeration and natural filtration, fish may survive for a few days to a week without a fish tank filter.

While fish don’t have lungs to take oxygen in from the air, they do have gills to obtain oxygenfrom water. Fish take water into their mouth and expel it through their gill passages, which allows dissolved oxygen to pass into their blood and to their cells.

Lack of Oxygen

If there is not enough oxygen in the water, fish will suffocate within a couple of days. That’s why you seldom see fish in completely still, stagnant waters in the wild!

As long as there is water circulation or oxygen injected into the aquarium water via an air pump or airstone, fish will be able to breathe, allowing them to survive for longer if the fish tank filter has stopped working.

Tank Waste

In addition to creating an organic habitat for your fish, live plants aid with the filtration process by absorbing ammonia, nitrite, and nitrate.

During the day, plants photosynthesize by using light as energy to convert carbon dioxide (a byproduct of respiration in fish) into oxygen.

However, this process is reversed at night when there is no light, which means live plants absorb oxygen and release carbon dioxide.

Can an Aquarium Work Without a Filter?

Aquarium Without Fish
Aquarium Without Fish

It’s possible for an aquarium to work without a filter, but it can be difficult to set up correctly. You’ll need plenty of real plants to help increase oxygen levels in the aquarium and maintain good water quality.

However, you’ll need to ensure the plants can keep up with the bioload of the aquarium, so be careful not to overstock the tank or select fish species that produce a lot of waste, such as goldfish and plecos.

Bioload

Opt for small fish species with low bioloads like ember tetras, white cloud minnows, and guppies. Shrimp can also work well in filterless tanks and help keep the tank clean by eating leftover fish food and algae.

Although plants will assist with maintaining oxygen levels and good water quality, they cannot remove debris. You’ll still need to do regular water changes to stabilize your water chemistry.

Most aquarists perform a weekly partial water change, removing around 25% of the aquarium water and adding fresh dechlorinated water to the original water level.

Use an aquarium water testing kit to keep an eye on your parameters like pH, nitrate, ammonia, and nitrite levels.

NOTE

Due to their complexity and difficulty, filterless aquariums should only be attempted by experienced fishkeepers. It’s much safer and easier to use a fish tank filter in an aquarium.

Why Is My Fish Tank Filter Not Working?

Fish tank filters can stop working for a number of reasons, including a clogged motor or intake tube, faulty components, unplugged wires, missing parts, and more.

Here are some signs to look out for if you suspect your fish tank filter has stopped working or isn’t doing its job properly.

How to Tell Your Fish Tank Filter Isn’t Working

Aquarium Water Bubbles
Aquarium Water

High Level of Ammonia and Nitrates in the Water

If there are high levels of toxins like ammonia, nitrite, and nitrate in your water, it’s very likely that your filter is not working or there is an underlying problem with your tank.

Ammonia and nitrite levels should always be zero in a healthy aquarium, while nitrate levels should preferably be between 5 to 10 ppm or at least below 20 ppm.

Overstocking, overfeeding, uncycled aquariums, dead fish, and decaying plants can all contribute to high levels of ammonia, nitrite, and nitrate.

It’s a vicious cycle that can lead to you having to say goodbye to your pets earlier than you should have.

No Suction

Fish tank filtration systems that are not working as intended often have a loss of suction or no suction at all.

When this happens, it prevents water from entering and exiting the filter.

A common cause for a filter that has little to no suction is a clogged impeller or motor.

No Sounds – or the Wrong Sounds

Aquarium filters that produce a grinding noise, heavy vibration, or even no sound altogether can mean there is an issue with the device.

Most fish tank filters will make some sound, even those that claim to be completely silent, but it’s usually just a gentle hum.

If your tank filter has stopped making any sounds or started producing an alarming noise, there may be a problem with it that needs addressing.

Common Problems and Solutions

Below are some of the most common problems why fish tank filters stop working and how you can solve them.

Filter Not Working Entirely

If your fish tank filter is suddenly a non-working filter, it could be due to a power surge, a clogged motor or intake tube, a problem with the connective cables, or a burnt-out/broken motor.

Solution

Check for clogs inside the filter, including the motor, intake tube, and outtake tube. Listen for any odd noises and vibrations.

Leave your filter unplugged for a few hours to see if the issue was due to a power outage. In contrast, make sure the plug is definitely connected to a power source. This is a pretty common issue but is very simple to resolve – just put the wires back in place.

You’ll be surprised at the number of times I’ve thought my filter was faulty only to discover that I didn’t have it plugged in properly!

Other Causes

If both of these solutions don’t fix the issue, there may be a problem with the filter’s electrical components, such as damaged wires and pins. At this point, you might want to consider buying a new filter unless you have experience in fixing electronics.

No Suction

As mentioned earlier, if your filter has no suction, there is most likely a clog somewhere down the line. Debris like small rocks, sand, algae, plant matter, etc, may have built up inside the device, causing it to lose suction and stop working as a result.

You will likely hear a grinding noise emitting from your filter if it is clogged.

Broken Motor

Alternatively, the impeller or motor in your fish tank filter may be broken or damaged. The motor in a filter gives power to the impeller so it can suck water from the tank, pass it through the filter media, and deposit it back into the aquarium.

When either one of these is not functioning properly, it can cause the filter to lose suction.

Solution

Fortunately, if your fish tank filter has a clogged motor or intake tube, it’s usually straightforward to fix.

Unplug the filter and take it apart by following the manufacturer’s instructions and look for a clog inside the impeller shaft, intake shaft, filter media chambers, and outtake tube.

If you spot any debris, algae, or gunk that has built up inside the impeller housing or intake/outtake tube, try to dislodge it with your finger or something long and thin (a clean drinking straw is also a great idea for removing blockages!).

Rinse

Cleaning Water Filter
Cleaning Water Filter

Give the rest of your filter a good rinse in old tank water and then reassemble it. Plug your filter back in to see if it is working properly.

If your fish tank filter still doesn’t have any suction, the motor and/or impeller may be damaged or broken. Check to see if your filter came with a spare part, otherwise order replacement parts or consider buying a new filter.

Flow Rate Too High/Low

The flow rate in your filter helps create water circulation to aerate the tank, but if it is too low or high, it can be a big problem. A water flow rate that is too high will make it difficult for your fish to swim, especially if they prefer slow currents.

All fish require different flow rates, so check the preferences of the species you own to make sure your filter provides what they need.

On the flip side, if the flow rate is overly low, it will not produce enough water circulation to oxygenate the tank.

Solution

If your filter’s flow rate is too high/low, check to see whether it can be changed – some filtration systems have an adjustable flow rate so you can change the output of the filter.

If you can’t, you might need to invest in a more powerful filter that comes with an adjustable flow rate.

An overly low or high flow rate isn’t usually an issue with the filter itself, but an issue with not having the right filter for your tank.

Reasons Why Your Fish Tank Filter Not Working

If your filter has suddenly stopped working or lost its efficiency over time, it could be due to one or some of the reasons below.

Clog

Aquarium Filter Maintenance
Aquarium Filter Maintenance

As mentioned previously, a clogged filter is one of the main reasons why fish tank filters stop working, but it also has a simple solution. Unplug the filter and remove any blockages like sand, algae, and gravel in the motor, intake tube, etc.

Rinse all the parts off in old tank water, then put the filter back into the water and plug it back into the power source to see if the issue has been resolved.

TIP

Make sure your filter is submerged in water before you turn it back on, otherwise it can burn out the motor.

Broken or Missing Impellers

Filters with a broken or missing impellers will be unable to provide adequate filtration, so you should look into fixing or replacing them as soon as possible.

Some filters come with spare impellers, but don’t worry if yours didn’t include any.

Simply order a replacement impeller for your specific model and remove the broken impeller.

Here’s how to find the locate the filter impeller.

How To Fix Broken, Stopped, Rattling, Noisy Filter Pump in Aquariums and Ponds

Unplugged Wires

If your filter isn’t clogged or doesn’t appear to have broken/missing impellers, the next method is to check for unplugged wires.

Make sure the wires are all connected to a power source (power strip, extension cord, electrical outlet).

If you spot anything unplugged, just pop it back into place and you’ve found your solution!

Damaged Wires and Pins

Torn, chewed, or damaged wires and pins will also prevent a filter from working and, unfortunately, it’s not as easy a fix as some of the other issues.

If you know what you’re doing when it comes to electronics, you may be able to repair or replace the wires and pins.

However, in most cases, the only solution to this common problem is a new filter.

Failed or Turned off Power Strips or Electrical Outlets

A non-operational filter could be due to a fault in your power source, so examine the functionality of your electrical outlet, extension cord, power strip, etc.

Plug your filter into a different power outlet or power strip to see if the problem is still present.

What Should Be Your First Concern When Your Filter Breaks Down?

Aeration should be your first concern when your filter breaks down….

Aeration should be your first concern when your filter breaks down. While fish can survive without a filter temporarily or altogether in some circumstances, they cannot live without oxygenated tank water.

If your fish tank filter breaks, use an airstone or air pump in your aquarium to increase water movement and add aeration.

Battery-operated air pumps are also available online or some pet stores if your filter is non-functional due to a power surge.

Final Thoughts

I hope I helped you understand some of the most common reasons why aquarium filters suddenly stop working and, hopefully, solved the issue with your filtration device.

Remember, an aquarium filter not working can be caused by blockages, unplugged wires, damaged motors/impellers, and faulty power, so be sure to check for these problems!

If you know any other fishkeepers or fish fanatics, make sure you share this post to help them with all their filter needs. And if you’re after more aquarium equipment advice, check out my other useful guides here.

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Mollie Newton
Mollie Newton
Founder of PetMeTwice. I love all types of animals from fish to fluff-balls! I also enjoy writing short stories and helping train animals 🤩