Why is Your Fish Tank Filter Not Working Properly

By Eddie Waithaka @aquariawise

Why is Your Fish Tank Filter Not Working Properly

As a fish tank owner, you know a filter working is essential to keep your tank healthy and your fish alive. Unfortunately, some filters stop working properly for no apparent reason.

Or so you assume!


There could be several reasons your fish tank filter is not working as expected. One possibility is that the filter is not getting enough water flow. If this is the case, you might need to adjust the filter position or increase the water flow rate.

Another possibility is that the filter is clogged. In this case, you will neeed to clean the filter. A damaged or stuck impeller, dead motor, a damaged power port (or stripe), and clogged hoses (or media trays) can also cause your filter not to work.


In this post, we’ll look at these and other possible reasons your filter may stop working and suggest some solutions.

See the rest of this post below.

Why Did Your Fish Tank Filter Stop Working

As we’ve seen above, there are several reasons fish tank filters stop working. Most causes are easy to solve, but in some instances, you may need to disassemble your unit, replace some parts or buy a new filter.

Now, let’s explore some of the possible reasons!

Zero or Low Voltage from A Power Source

You may be surprised by the number of tank owners that forget to plug in their fish tank filter when setting them up.

So, ensure your filter unit is plugged into a power source before you start it. Check that the wall plug-ins and power strips have not failed and the filter is getting enough voltage.

At times, individual sockets burn out, so if your https://aquariawise.com/fish tank lights are working, use them to test the socket (or the strip) your filter is plugged into.

An old or damaged power strip may cause a voltage drop and keep the filter from working. So, start by plugging your filter into the socket to ascertain the extension is not the problem.

If your filter is coming on briefly, buzz, then goes off, especially when you push the plug point into the sockets or extension, your filter may have loose connectors or parts of the wall plug-ins are moving around.

There might also be other problems with the power source or connector cables, such as blown fuses, a tripped breaker, or a broken cord (or wires), most of which can be easily fixed or replaced.


If you are in the market for a perfect power strip for your aquarium, I suggest you try Tripp Lite 7. I guarantee it will serve you well but protect it from runoff water from the tank or filter.

Mount your strip to avoid using it on the floor with everything going around your fish room. Block off unused sockets with a piece of tape or child safety plug covers to keep water out of the strip.

Stuck or Damaged Impeller

Impellers are crucial in fish tank filters as they help circulate the water. If the impeller in your filter is the problem, the unit will only make a grinding noise, but there will be no flow.

Inspect the impeller to ensure that it is functioning and that no debris is blocking it from rotating. You may also need to disassemble the filter to check for broken parts.

Replace damaged parts, clean the impeller (intake hoses), assemble, plug, prime your filter, and start it. If the impeller was the problem, your filter should work.

Moving forward,…

Remember to inspect the impeller regularly to ensure that it is functioning efficiently and no debris is keeping the filter impeller from rotating.

Clogged Fish Tank Filter

One potential issue with keeping fish in a tank is that their waste can clog the filter. This can be a problem if there are a lot of fish in the tank or the filter is not very efficient for the tank size or stock you have.

Ideally, you will only need to clean your filter once a year, but in some cases, it may be necessary to clean the filter more often than usual to prevent it from becoming clogged.

Filters in fish tanks with live plants, a light sand substrate that is easy to blow up, or messy fish that forage or leave a lot of uneaten food tend to clog more often and need frequent cleaning.

A jammed or clogged filter will be hot and make a buzzing sound.

To confirm,…

Place your hand in inside the filter container while plugged in. If the temperature in the unit is high and you can hear the motor buzzing, but you are not getting any flow from your filter, it is most likely clogged.


Most fish tank filters use a motor to operate an impeller that creates a suction and draws water from the tank through intake tubes and filter media inside the filter housing.

Consequently, the impeller, intake tubes, and filter media are most likely to clog and cause your filter to stop working, and that is where you’ll want to start while cleaning the filter.

ENSURE YOU FOLLOW A STRICT PROCEDURE WHEN CLEANING YOUR FILTER to avoid killing beneficial bacteria colonies necessary for your tank’s biological filtration.

Only rinse the filter media to remove gunk and solid debris. Do not use any detergents.

If you must replace the filter sponge, leave the new media with the old one in the tank for several weeks before you tose the previous set.

This will help bacteria colonies grow into the new filter media from the old sponge.

A Dead Filter Motor

A motorized fish tank filter is a crucial piece of equipment for any home aquarium. It helps to keep the water clean and healthy for the fish.


If the motor on the filter dies, the filter will stop working. The tank will become polluted, and the fish will die. There are a handful of things you can try to do to revive a stalled fish motor or (and) to confirm if it is dead.

First, check to see if the filter is plugged in and receiving power. If it is, try unplugging it and plugging it back in. If that doesn’t work, vacate the filter from the power source, and wait a few hours before placing it back.

A power surge can cause a filter to go out and come back after several hours, but it can also fry the motor and force you to buy a new filter.

No Suction or Improper Flow

If your filter is not pulling enough water from the fish tank, there will be an improper flow rate, and the unit won’t work as expected.

There could be a few reasons your fish tank filter is not sucking in water. One possibility is that the filter is not attached to the tank properly. Another prospect is that the filter is clogged and needs to be cleaned.

If you have a HOB filter, ensure it’s well positioned for your filter pump to suck it into the filter body. Raising the water level in the fish tank may also help start a stalled hang-On-Back filter.

If a canister fish tank filter has stopped working, inspect the system for clogs and blockages and clean any gunk you find. Once you are done cleaning, start by priming your filter.

Fill the filter reservoir and inlet hose with water to reestablish a flow. Place the inlet inside the fish tank and start your filter.

If there is no other issue causing it to malfunction and the filter is getting enough water, it should start cleaning your fish tank immediately.

Bare in mind that if the hoses are too short or the attachment parts are not tight enough, you will have limited suction and flow.

Loose hose attachments or a broken tube will let air in and reduce the flow rate.


Ensure your filter is placed at a lower level than the fish tank. The flow rate will gradually decrease as the height margin between the tank and filter unit reduces.


Check that your flow rate is set and adequate for the level of filtration you require.

How Do You Know Your Fish Tank Filter isn’t Working

One way to know your fish tank filter is not working is if the water is not circulating around the tank and filter unit. Another way you can tell a filter is not working is if the water is not being cleaned.

If there are sudden ammonia spikes from water tests and you can see a lot fish of waste and leftover food floating in the water or spread on the substrate, your filter is most likely not working.

A working fish tank filter will also make a buzzing sound from the motor and splashing or waterfall noise inside the unit or aquarium if you have a HOB unit.

A working fish tank filter will also create surface agitation on the water surface as clean water from the filter unit pours into the fish tank.

That said,…

A fish tank filter is a complex piece of machinery, and there may be some issues you may not be able to fix on your own.

A professional can troubleshoot the problem and fix it quickly and easily.

That’s all for this blog post. Hope it was helpful. See you at the next one.

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