7 Reasons The Fluval FX6 & FX4 Canister Filters Are Beasts! Full Review

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With that out of the way.

The Fluval FX6 and FX4 are beasts and they won’t let you down.

The Fx6 looks like someone took a shop vac and converted it into a canister filter, this thing is absolutely HUGE! The FX4 is pretty big as well.

But before we get into the details of the review, here are just 3 of the key features these monsters offer;Fluval Canister Filter, FX4 Filter (250 Gal)

Self-starting canister filter: Just add water and plug it in. The filter does the rest. No more siphoning water, no more push button priming this filter does everything itself.

Smart Pump Technology: Every 12 hours the filter will stop, allow any trapped air to escape, and then restart. This ensures the best filtration efficiency at all times.

Seamless Water Changes: The FX6 & FX4 both feature a utility valve at the base of the unit which can be used to empty the unit and complete your water changes by draining and refilling right from the valve.

In this review, we’ll talk about some of the key features that make this beast a top performer for the price point and one of the best canister filters on the market.

The 7 Best Features Of The Fluval FX6 & FX4 That Make Them BeastsFluval Canister Filter, FX4 Filter (250 Gal)

  • Self starting feature, just add water and plug it in. The filter primes and starts itself. 
  • Easily lift out all 3 HUGE media trays for cleaning with “Tote Handles” that pull out.
  • Energy efficient motor assembly uses 10% less power than previous models.
  • Quickly do water changes and clean your gravel: just attach a hose to the utility valve located at the base and the filter does the rest. When your done you can store the extra hosing with the easy storage clips located on the canister lid. Check out the video below for a demonstration.
  • Prevent leaks with large locking clamps that secure the motor and canister in place.
  • Every 12 hours the filter will stop, allow any trapped air to escape, and then restart. This ensures the best filtration efficiency at all times.
  • Don’t worry about problems it comes with a 3 year warranty and built with heavy duty construction.

The best feature of the Fluval FX6 (Update July 6, 2016)

Is the ability to attach the all-new Fluval FX Gravel Vac (compatible with FX4, FX5, and FX6 model filters), which offers powered and convenient substrate cleaning for your aquarium.

Watch this video showing how the FX6 simplifies cleaning your gravel.

From Fluval Aquatics

Quick Overview Of The Fluval FX6 & FX4 Canister Filters

Fluval Canister Filter, FX4 Filter (250 Gal)Get The Fluval Canister Filter, FX4 Filter


  • The massive Fluval FX6 canister filter is a multi-stage filter that is good for fresh and saltwater aquarium up to 1500 L (400 US Gal).
  • One of the great features of the FX6 is its highly efficient motor which consumes 10% less power than the FX5.
  • The FX6 brings back the smart pump technology from the FX5 models which stops the filter every 12 hours to maintain optimal filter performance.
  • The intake tube is telescopic so you can adjust the length to your tank and also has an anti-clog strainer to keep the water flowing.
  • Everything from the valves, media tray, intake/outtake tubes and the canister itself are all well-built and super durable.


  • Not many changes from the FX5. BUT it’s difficult to improve much on an already brilliant filter.
  • The size of these units means you need a large place to store them. However, when you think of the filtration capacity these beasts provide it’s worth the trade off.

First off the FX6 is an awesome filter but if you already have an FX5 then there is really no need to upgrade.

The main changes are color aesthetics and the fasteners used to be rubber.

However, if you are looking for a new filter and the price for the FX5 & FX6 are within the same range, then I would suggest you go with the FX6.

In my opinion, it’s the best canister filter made right now, if you have the money and you want a filter that does everything itself then the FX6 is the way to go.

Is The Fluval FX6 Quiet?

For being one of the largest canister filters with a huge pump the Fluval FX6 is very quiet. As with most filters and powered equipment, there is a low humming that is only detected when close to the aquarium.

Seamless Water Changes (Update July 6, 2016):

Fluval recently updated the FX6 & FX4 with a built-in water change system, multi-stage filtration, enhanced media capacity and even an optional powered FX Gravel Vac with independent filtering capability.

Check out this video showing all the new features of the Fluval FX6 & FX4

From Fluval Aquatics

What Comes With The Fluval FX6 & FX4 – What’s In the Box?

So What Comes With The Fluval FX6 & FX4? Well, to be honest, everything!

It includes all the pipework, attachments and all the filter media you need to simply plug it in and watch the filter do the rest.

The Fluval FX6 & FX4 comes with a 3-year manufacturer’s warranty.

Here’s the list;

  • Ribbed Hosing
  • Rim Connectors
  • Strainer
  • Output Nozzle
  • AquaStop Valves
  • Canister
  • Utility Valve Hosing
  • Pump Unit (Motor) Power Cord
  • Media Baskets
  • Filter Lid & Accessories

Included Media:

  • Foam
  • Bio Foam
  • Biomax Ceramic Rings
  • Carbon Pad
  • Media Bags

You can also check out this Fluval FX6 unboxing by Stuff & Us. Then continue reading below to see how to set up this filter.


This is the easiest canister filter I have ever set up.

As soon as you plug the filter in, the canister fills with water from your aquarium.

It pumps for 1 minute, pauses for 2 minutes to evacuate air from the system, then immediately begins the filtering process.

Check out this video from Big Al’s where they go over some of the key features, but then show you how easy it is to set up this beast of a canister filter.

Fluval fx6 media setup:

The Fluval FX6 comes with all the media you will need to run the filter, refer to the product list above for all the media included.

The FX6 comes with 3 huge media trays which all have circular sponges around the perimeter from the top to the bottom around 2″ thick. The FX4 to contrast has only 2 trays.

Here are two cross sections of both filters so you can see how the media stacks up when comparing the two filters.

Fluval FX6 3 Media Trays
Fluval FX4 2 Media Trays

It’s also important to note that Fluval has provided a Basket in Basket media tray design which effectively allows you to provide up to 6 stages of filtration for the FX6 and 5 stages of filtration for the FX4.

Here is a breakdown of each tray and the 6 stages of filtration possible with the FX6;

Top Media Tray #1

  1. Bio Foam
  2. Bio Foam
  3. Foam

Middle Media Tray #2

  1. Bio-Max Rings
  2. Bio-Max Rings
  3. Foam

Bottom Media Tray #3

  1. Carbon Pad
  2. Foam

This may look like 8 stages, but the Foam is counted as one stage as it sits in the outer ring of each tray and when stacked (See the pictures above) forms one continuous stage of mechanical filtration.

Here is a suggested set up for the tray’s that could work well.

However, always do your own research to ensure the media you use won’t harm your fish.

  • First tray: Clearmax and Purigen
  • Second tray: Pond matrix
  • Third tray: Chemi pure
  • Bottom: Filtering pad for polishing, same on top.

Tip: To get your water really clear use Poly-Fil. Make sure that it’s 100% polyester. You can get this stuff really cheap on amazon. Then simply surround your media with this stuff. Lay it on top as well.

The Fluval FX6 gets amazing ratings in all categories and all stores, it may seem perfect but it does have some problems which are why we compiled a huge troubleshooting guide to fixing the most common Fluval FX6 problems.

Check out some of the ratings below.

You can feel confident that you are picking a winner, whether you are a buying your first canister filter or if you’ve been around the block a few times.

Fluval Canister Filter, FX4 Filter (250 Gal)Get The Fluval Canister Filter, FX4 Filter

Further Reading: Need Help Finding A Canister Filter? Our Guide Can Help You Find The Best Canister Filter For Your Aquarium And Your Needs. We’ve Reviewed All The Top Brands From Fluval, Ehiem, API, Marineland, And More.

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