Fluval FX 6 and FX4 – High Performance Canister Filters Review

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Looking for a powerful canister filter for your Aquarium, Fluval FX series Canister Filter is definitely the one for you. Made with precision and an objective of providing the best, Fluval FX6 is built to provide a filtration for up to 400 US Gal. Read on to know more about the filter.

High Performance Delivered

With a multi-stage filtration unit and a powerful motor unit, the filter provides promising results. You will be amazed by the clarity of the water, post filtration. While our Fluval FX6 review for a 350-gallon aquarium the filter was able to clean the tanks murky water, eliminating even the tiniest contaminant.

Fluval has designed the FX6 and the FX4 to accommodate more filtration media using less space. Fluval FX6 has 6 media compartments, while the FX4 has 4 media compartments making enough room for the media. And with a variety of stock media that comes with the filter, you do not have to get additional media.

The flow rate of the filter is very good and maintained till the end of the maintenance cycle. Since the water passes through the outer foam first, larger debris is eliminated maintaining the flow rate and preventing clogging of inner media.

Setting up the filter

You don’t have to be worried about the filter setup, rest assured the filter setup is quite easy.

  1. Unpack the media and wash them before use, and place them in the media basket.
  2. Fix the media baskets with the T-Bar and place it in the Canister.
  3. Close the lid after adding water in the Canister. (Adding water is to help in Priming the filter) and secure it with Easy grip locking system.
  4. Cut the hose to the required length for inlets and outlets connections. And connect it to the Filter
  5. Attach the intake strainer and output nozzles, place them in the Aquarium using the suction cups.

Switch on the Filter and you good to go.

Priming the Filter

Fluval has ensured that the priming remains effortless and less of a pain. With a smart pump technology, the Filter takes care of the priming. Just add water in Filter while closing the lid and start the Filter. The Filter would run for approximately 2 minutes shut down automatically remove air bubbles and then automatically restart.

Filter Operations and Specifications

Fluval FX6 Maintenance Dials

While it comes to operations, the FX series filters are extremely quiet while running.  The precise-engineered bearing ensures that you do not hear even a slightest of hmm. With the Leak Proof design of the media basket, leakage is avoided ensuring there is no bypass.

 Fluval FX series filter could be used for Freshwater and Saltwater Aquariums 


Smart PumpTM

The Fluval FX6 and FX4 comes with an advanced microchip technology called as Smart PumpTM that continuously monitors and optimizes pump performance. Smart PumpTM maintains the Impeller Speed and the Pump Power ensuring optimal flow rate throughout.  Also, the Smart PumpTM checks for trapped air and evacuated if any every 12 hours. This makes the filter Energy Efficient, for running at maximum power only when required.

To protect the filter from damage, a safety feature is included that would turn off the motor whenever impeller is impeded.

Following are the technical specifications of the FX series filters:

Product NameTank CapacityWattageFlow Rate
Fluval FX 6 External Filter400 US Gal41 W925 GPH
Fluval FX4 External Filter250 US Gal30 W700 GPH


The filter comes with a lot of handy functions that makes the maintenance hassle free just like setting up the filter. Many times we tend to forget the maintenance schedule, so the filter comes with a monthly Indicator dials so you never miss the next maintenance and water change date.

Additionally the purge valve at the bottom of the filter that could assist you in avoiding creating a mess while carrying out maintenance.

The Purge Valve

Utility Valve at the bottom of the filter

The Fluval FX series Filter comes with a unique feature of ‘Purge valve’ also called as the ‘Utility valve’ which comes in handy to avoid a mess.

It is a multi-purpose valve at the bottom of the Filter which could be used as a direct input or output. The Gravel Vac cleaning uses utility valve for the input, whereas you could empty the tank or refill it using the utility valve.

 Helps you empty the canister before moving it for maintenance. 

Here’s how you could do empty/fill your tank using the utility valve, avoiding the mess caused by manual siphoning.

  • Turn off the input and the output AquaStop valve
  • Attach a hose to utility valve with an output to the bucket or to drain.
  • Turn on the input aqua stop valve and the utility valve.

And similarly, you could fill in the tank using the. We found this approach quite convenient since there was hardly any water spillage and mess. And we are sure you would love it too.

Gravel Vac

Fluval FX series Gravel Vac

The Gravel Vac(Included in the newer models) is a unique add-on feature which is very useful for cleaning the parts of the Aquarium which are not reachable during normal filtration. Using an extended suction pipe, prefiltered and then let in through the utility valve. The water sucked in then goes through the filter media in the media baskets and finally clean water is back through the Filter outlets.


This a feature that you would find very helpful in maintaining the overall health of the Aquarium by eliminating plant debris, excess food, fish waste and much more. The fine filter pad is capable of cleaning even the finest of particle leaving you tank sparkling clean. This is a unique feature among the filters in this range.


With loads of features included, Fluval has thoughtfully designed this filter to provide a hassle free user experience making it a preferred choice. We would recommend Fluval FX4 and Fluval FX6 if you are looking for a Canister filter for aquariums in a range of 400 US Gallons.

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