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When you spend a lot of money on a piece of equipment you expect it to be flawless. However, nothing is perfect and although the FX6 canister filter from Fluval is close to perfect, it does have some common problems that don’t seem to go away.

We’ve tried to help out any new owners of this awesome filter, by compiling this guide to fixing the most common Fluval fx6 problems.

Before we get into the guide if there is one thing you should do is watch the following video directly from Fluval.

The list covers most of the common issues people have with the Fluval FX6 and FX4 canister filters along with very easy troubleshooting tips and videos so you can fix your filter fast.

Watch Fluval FX6 Canister Filter Troubleshooting & Maintenance Tips.

Fluval FX6 Canister Filter Troubleshooting & Maintenance Tips.

As you can see it’s very important to complete any preventative maintenance and on-going care for this expensive filter.

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Fluval FX6 Preventative Maintenance List

To recap, here are just some of the main points in the video, which should keep your filter running smoothly.

Take Care of Your Hoses

Your hoses and tubes can get clogged with debris over time so be sure to clean them out at least 3 times a year. Also make sure your hoses are not kinked, bent or looping.


Always use a silicone lubricant after any maintenance. As you know this beast of a canister filter moves a lot of water and using the lubricant helps prevent any leaks.

Use Filter Media Bags

If you intend to use any media that is made up of small granular particles, be sure to place it in a bag. Loose bits can get trapped in the pump and stop your impeller from working.

Replace Old Impellers

At some point, the impeller will need to be replaced. If you notice any vibration or loud noises this could be a sign you need to replace the impeller. When you purchased your FX6 there would have been a replacement impeller box included.

Now let’s get into the troubleshooting tips.

Most Common Fluval FX6 Problems and Troubleshooting Guide

Startup Issues – My Fluval FX6 Will Not Start?

One of the most common problems with the FX6 filter is that after cleaning the FX6 will not startup.

There are many reasons this could be happening below we have listed a few of the most common reasons the FX6 won’t start as well as the solution for each issue.

  • The impeller is jammed. Clean and rinse the inside remove all the filter material and baskets to remove any trapped sand or debris and take out and rinse the basket and impeller very well. Then reassemble and try again.
  • Media stuck in pump. Open the pump, remove any media that is stuck or jamming up the pump. Then reassemble and try again.

Fluval FX6 Motor Problems.

As long as you stay on top of your maintenance you shouldn’t have any problems with the motor.

However, here is a short video (again from Fluval) with some FX6 motor maintenance tips.

FX6 motor maintenance tips

My Fluval FX6 Keeps Turning Off?

Hopefully, you’ve read the manual and realize that your filter is meant to turn off every 24hours to purge. Any trapped air.

They typically shut down for about 10 minutes so don’t be alarmed.

Priming Issues – How to Prime the Fluval FX6 Properly

One of the main benefits of getting an FX6 canister filter is the self-starting & priming features. But what if you can’t get it going when you first set it up?

Here is a great video from Everyday Aquarist showing you exactly how to set up the Fluval FX6 as well as how to prime the FX6 filter.

How to set up the Fluval FX6 as well as how to prime the FX6 filter.

Noise Issues – Fluval FX6 Rattling & Shuddering?

A noisy filter sucks! And if you spent all that money on the FX6 I’m assuming you don’t want to hear it.

As with most fish tank equipment noise is one of the most common complaints and the FX6 is no different.

Here are the most common noise issues with the Fluval FX6 and how to silence them.

  • Debris/Substrate stuck in the impeller – Clean or replace your impeller
  • Debris/Substrate somewhere in the canister – Clean the entire canister system
  • Air is stuck in the canister – Similarly to issues with bubbles, you need to purge the FX6 or remove some media.
  • Air source too close – Similarly to issues with bubbles, you need to keep any external air sources as far away as possible. Or, create barriers between the air source and intake.

Air Problems – Air Trapped in Fluval FX6 Causing Microbubbles, Popping & Excessive Bubbling

The Fluval FX6 filters are very strong filters, so much so that they can suck up nearby air bubbles from air stones, other aquarium filters or protein skimmers.

However, there are a few other reasons you may be experiencing bubbling. Here are the most common reasons for this problem and how to correct the issues.

  • The intake is Too close to air stone, filter or protein skimmer – Remove all air producing equipment to be sure they are not the reason. If they are the source of the problem try to keep the intake as far away as possible from the air source. If not possible try to create barriers between the air source and intake.
  • It’s a new setup – Sometimes the self-purging feature takes time. Wait up to 48hours to allow the purging to complete.
  • You’ve used too much media – Don’t jam the media in tight, the Fluval FX6 works best if it’s not packed.

Flow Rate Issues – Fluval FX6 Low Flow Problem

Sometimes after setup, you may not be getting the desired flow rate or notice that you’re FX6 has low flow.

Here are a few reasons this may be happening along with the solution.

  • You’ve used too much media – Reduce the amount of media you are using to ensure water can flow through the canister as intended.
  • Your impeller may be jammed – Remove and clean the impeller.
  • Your hose may be clogged or blocked – Check all hoses to ensure they are free and clear of any restrictions.

Pump Issues – Fluval FX6 Impeller Cleaning Tips

The following video is an easy way to ensure your impeller is clean and will start without any problems.

Fluval FX6 Impeller Cleaning Tips

Further Reading: If you’re looking for more great filters consider checking out our review on the New Fluval 07 Series Canister Filter which is a seventh-generation product with more than forty years of history and noted as the best selling canister filter of all time.