Fluval FX – Review + Opinions

Hello intrepid reader, this time we are dealing with the “Beast” of external aquarium filters: Fluval FX Series.

The “beast” of aquarium filters
Multi-stage filtering system
Easy maintenance
Low consumption

In this review, we will talk about the key features that make this beast of a canister filter one of the best external aquarium filters on the market.

European research and development house Hagen has innovated in the aquarium filter market with the Fluval FX series. These devices are from another world if you compare them with the traditional internal filters for aquariums, from another galaxy.

The new external filters in the Fluval FX range use SMART PUMP TM technology, which takes filtration to a higher quality. This is thanks to complex multi-stage filtering that optimizes filter performance.

Its design includes an integrated system that facilitates heavy water changes. In addition, the «basket within a basket» system offers a greater capacity of filter loads and a more efficient filtration.

Click on the button below the image to see these filters on the Amazon website.

The Fluval FX series of external filters are known for their ruggedness, efficiency and outstanding power. The Fluval FX Series has two models that can accommodate large aquariums:

  • Fluval FX4 – Up to 1000 liters.
  • Fluval FX6 – Up to 1500 liters.

FX Series filtration is defined by the manufacturer as “multi-stage refined”. The water flow develops a sequential process that further purifies the water at each stage. This is much more efficient than when the water passes through all the filtration stages in one go.

In its design, it has been taken into account to facilitate the maintenance process. Fluval ‘s FX fish tank scrubber line has a multifunctional valve to drain and refill the tank from the bottom. This allows the aquarium to be emptied and refilled from the valve during water changes, without having to alter the installation or disturb the inhabitants.

Come on, join us and discover the beast of external aquarium filters.

Fluval FX canister filter

The Fluval FX external filter is a filter beast that will not let you down. The Fluval FX6 looks like an industrial vacuum cleaner turned into an external aquarium filter. That thing is HUGE! Whether it’s the big model or the small model, the Fluval FX-4 is pretty big too.

Before we get into the rest of the details, let ‘s take a look at the 3 key features these leak behemoths offer:

  • self-priming canister filter: simply add water and connect. Fluval FX does therest. No more siphoning water, no more priming button. This filter does everything by itself.
  • Smart Pump TM technology: every 12 hours the filter stops. It will allow any trapped air to escape and then restart. This ensures the best filtration efficiency at all times.
  • Seamless Water Changes – The FX features a convenient valve at the base of the unit. It can be used to drain the unit and complete water changes by draining and refilling directly from the valve.

The power of this series of Fluval filters offers a better and faster cleaning, since it traps more amount of debris. It also allows less frequent maintenance.

Fluval FX Series

As always, you’ll have the legendary FX Series combination of power and efficiency, allowing you to spend more time enjoying your aquarium and less time maintaining it.

Fluval has achieved with the FX series a product of the highest quality. With features specially designed for the aquarium, but also for the aquarist.

If you want to consider another type of filter for your aquarium, our article on the waterfall filter for fish tank explains everything about this type of filter. The filter hung from the side of the tank.

Before going on to see these canister filters in detail, you may be interested in seeing our category dedicated to lighting if you are setting up your aquarium. There we talk about the other factor of great importance in the biological balance of the tank, lighting.

Price and Technical Characteristics

fluval filter FX4 Features

The sale price of the fluval FX 4 filter RECOMMENDED BY THE MANUFACTURER on its website is €279.95.

fluval filter FX6 Features

The selling price of the Fluval FX6 RECOMMENDED BY THE MANUFACTURER on its website is €364.15.

Fluval FX Series Features

We will continue to see in depth all the exceptional characteristics of these external filters for aquariums from the Fluval house. But before we get into the details, let’s take a look at Fluval ‘s video for their FX Series.

After this video, you realize that you cannot compare this beast with internal aquarium filters or backpack filters. They are all aquarium filters, but they play in very different leagues.

Now, let’s see the most interesting details of this Fluval external filter for large aquariums.

Smart PumpTM Technology

Smart Pump TM technology is patented by Fluval and uses an electronic circuit that continuously controls the pump. This brings the following benefits to the Fluval FX filter:

efficient energy performance
The force and speed of the impeller are constantly monitored to obtain the maximum power with the best energy efficiency. This allows efficient energy use that uses 10% less energy than previous models.
auto restart
Every 12 hour period the FX filter stops, evacuates any air that may be trapped, and then restarts. This ensures the best filtration efficiency at all times.
Automatic priming and starting

The auto-priming feature is very convenient, avoiding the tedious job of priming the filter system.

In the Fluval FX series filters you just have to add water and connect it. The filter is self-priming and starts by itself thanks to this Smart Pump TM technology.

Multifunctional Valve

The Fluval FX series has a multifunctional valve that, together with the hose, is very useful to facilitate regular water changes. It is very practical and easy to empty and refill the container during maintenance. Click here to see the replacement for this valve on Amazon.

Water changes and gravel cleaning are done quickly and easily. Simply connect the hose to the multi-service valve located at the base and these fish tank filters do the rest. When finished, the hose is collected with the clips located on the lid of the container.

All this means that the multifunction valve system provides 3 very notable benefits:

  • Save time.
  • It requires less work.
  • Avoid clutter.

Fluval FX Filter Loads

The Fluval FX external filter comes with all the necessary filter media to provide the highest quality filtration.

Fluval has designed trays to provide multi-stage filtration. It has 6 stages of filtration for the Fluval FX6 and 5 stages of filtration for the Fluval FX 4.

The Fluval FX4 comes with 2 huge media trays that have circular sponges going around the entire perimeter. From the top to the bottom.

The Fluval FX6 in its case, has 3 trays to cover aquariums up to 1500 liters and 6-stage filtration.

The filter media provided in the Fluval FX Series are as follows:

Fluval FX Series Filter Media
Media river filter FX4 river filter FX6
Foamex pre-filter 4 6
Bio Foamex 1 two
BioMax two two
Foamex Carbon 1 1
bags two two

The baskets for the filter loads have a large capacity, housing a large volume for these media. This allows to form a large colony of bacteria that keep the water well purified. Our article cycling an aquarium explains everything you need if you have any questions about this basic topic.

In addition, they allow these loads to be configured in a totally personalized way, according to the needs of each aquarium.

Finally, the baskets have practical T-shaped handles to make filter maintenance as easy as possible.

Compatible with Fluval FX Gravel Vac

One of the coolest features is the ability to connect the new Fluval FX Gravel Vac, the vacuum cleaner for gravel from the aquarium substrate. Click on this link to see the offer of this vacuum cleaner in the Amazon online store.

This aquarium substrate cleaning accessory is a siphon that connects to models FX4 and FX6 (2nd generation).

In addition, it has its own filter bags to further facilitate and optimize cleaning, a simple flow control, anti-clogging barrier…

Other features

  • Silent operation. The impeller has a minimum of mechanical seals to reduce noise to a minimum.
  • Multidirectional outlet mouths. Specific flows can be created in the tank thanks to its double outlet nozzles.
  • Anti-clogging and telescopic inlet mouth. To ensure a regular flow, the inlet has an anti-clogging grille. In addition, it is telescopic, to adapt to each aquarium.
  • Suitable for fresh or marine aquariums. This filter is suitable for a freshwater aquarium and for a marine aquarium as well.
  • Aquastop valves. These handy valves achieve a quick and leak-proof connection thanks to Click-fit technology.
  • 3 year warranty. No problems to worry about, it comes with a three-year manufacturer’s warranty.

Opinions, reviews, ratings, reviews and reviews

On there are not many opinions from customers who have decided to buy their fluval FX filter in this online store. There are only eight reviews at the time of writing this article, but the ratings are close to the maximum mark. Seven reviews give five stars out of five, and the other four because it seems a bit noisy.

From the reviews on, we can see that both models get practically the same grade, an excellent. Although it is true that there are reviews that should be read in our beginner aquarium article, it is well worth it to get a general idea.

Let’s see a summary of these opinions on Amazon:

Fluval FX4 reviews

On the positive side, customers highlight the effectiveness of the filter, highlighting the crystal clear water in their aquariums. They also value the power of its pump and its quiet operation.

Others have appreciated the self-priming feature, as well as the ease it provides when performing water changes. There are many positive features that customers highlight about this filter.

But there are also negative reviews. A user complains of a continuous drip at the outlet connection; but more serious, another tells that after a week the filter burst, causing several damages. Another customer claims that after 5 months the engine stopped.

In another review, the customer accuses the filter of spoiling his aquarium, even harming the fish. He also complains about customer service not providing good service.

Another couple of bad experiences close the list of negative opinions about this series of filters.

Fluval FX6 reviews

The positive reviews also highlight many of the features of this model, just like the FX4.

From its excellent work filtering the aquarium water, to its easy cleaning. From its silent operation to the volume for the filter media. A long list of good opinions about this filter “beast”.

Among the negative evaluations, some user criticizes the design, which finds both screws cumbersome.

Another complains that the pump stopped working after a year. There are also those who expected more power from this filter.

Advantages and disadvantages of Fluval FX

Advantages of Fluval FX filters

  • It is a multi-stage composite filter that is excellent in both a saltwater and freshwater aquarium.
  • One of the great features of the FX is that its highly efficient motor consumes 10% less energy than previous models.
  • The FX offers the “Smart Pump TM technology from previous models that stops the filter every 12 hours to maintain optimal filter performance.
  • The intake tube is telescopic so that it can be adjusted to the length of each tank. It also has an anti-clogging filter to keep the water flowing.
  • All the components, from the valves to the media pan, the inlet/outlet tubes and the bowl itself, are well built and super durable.

Disadvantages of Fluval FX Filters

  • The size of these units means that a large place to store them is necessary. However, when you think about the filtration capabilities these beasts provide, it’s well worth it.

Other External Filters


There are many features that we have seen of these filters, which provide multiple advantages. Advantages for the health of the aquarium, and advantages for the aquarist.

Looking at the opinions of users about these two filtration “beasts”, it is quite clear that we are dealing with the superior range of filtration devices for medium and large aquariums.

If you are looking for quality and comfort, the Fluval FX4 and Fluval FX6 filters are one of the most important options. Forget about cleaning the filter for months, and enjoy the crystal clear water of your aquarium with the «beast» of filters.

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