Saturday, 2 March 2013

Our review on Fluval FX6

After recently installing 2 x Fluval FX6 external filters on a huge 2500 litre cylinder aquarium we are sharing our opinion and thoughts on the FX6 during and after installation

The aquarium: 2500 litres acrylic cylinder aquarium measuring over 4ft on diameter and 5ft in height.

Due to the height of this aquarium we needed an external filter that could cope with a height of 1.5 m to the top of the water to the top of the external filter. After much research the only external filters we could find that would work was indeed the Fluval FX6. This was great news as we have used the Fluval FX5 on many installations and in our opinion for good quality beefy externals that can cope with high waste and through water around, these filters are hard to beat. So it was decided to use the Fluval FX6 x 2.

First impressions of the FX6 did not let us down. The Fluval packaging is excellent, clearly labelled with all the key features such as :-
Self priming with smart pump technology! This smart pump will actually alter the flow rate if needed and upon installation will cut out to evacuate any trapped air, this handy feature also works every 24hrs
New maintenance dial reminders so you can make a note on the filters when you last did a water change or last did a service on the filter
The FX6 seemed to have all the great benefits the FX5 came with such as drainage port at the bottom of the filter,
Self priming plug and start
Aquastop Valves
Multifunctional Rim Connector
ClogProof Strainer
Two MultiDirectional Output Valves

So first impressions where good! Upon unpacking the FX6 we noticed there was not the instructional DVD like there was with the FX5 however it did come with excellent step by step instructions which where very clear. Luckily we didn't need them as setting up was very similar to the Fluval FX5.
It has a nice black sleek design and it truly does look like a very high quality product.
All other connections look the same as the FX5 with very robust quick release connections on the inlet and outlet, both of which with robust taps on, a handy device especially on this installation as our drains will remain flooded so need to be able to shut off the water when needed.
The new maintenance dials are a good idea. They don't count down and bleep or light up or anything to let the user know of when either a water change or service is due on the actual filter so you have to remember to adjust the dial to which month you carried out the task. There is a dial for water changes and one for the filter with a robust click setting so you can point the dial to 1 - 12 months to show what month the task was carried out. We think this would have been better with a month and also date facility so the user can set the actual date not just the month. Some aquariums demand more frequent water changes or filter servicing so a more accurate date setting would have been better. Also a count down dial would have been good such as number of days to the next water change or service on the filter which then maybe lights up or beeps to signal when the countdown timer ends. On the other hand though it is a handy feature.
Flow rates are very similar so everything looks ready to go.

Installation : another great benefit of the Fluval FX6 is they come with Biomax media! Unlike the Fluval FX5! It has circular sponges around the perimeter of the inside of the filter housing from the top to the bottom around 2" thick. Then in the middle there are three huge media baskets. The bottom one with a sponge and room for more media, the central one is packed with biomax and the top basket packed with sponges for the final filtration before returning to the aquarium. We gave the biomax a good rinse inside the Fluval media bags which are also provides making sure no small particles of biomax could not get inside the main filter to cause damage to the impeller. This is something Fluval highlights in their instructions and is very important, any bits of filter media or hard particles can get to the impeller and cause damage so make sure everything is inside the media bags provided. After a quick check over the top of the filter housing is screwed down with the many fastenings provided ensuring a solid tight fit of the lid, under 1.5m of pressure and 2500 litres of water it was reassuring to see how solid the fixings where!
As our drains where externally plumbed to the underside of the aquarium we could not use the provided Fluval hosing as in order to prevent any loops in filter hosing we only needed a small length of pipe from the drain fitting to the FX6, so we opted for the largest Eheim 22mm green hosing which is the perfect fit over the FX6 fittings and also our drain port.
The returns we used the Fluval FX6 hosing. This comes in one continuous length sealed with the connections at both ends, designed to be cut so the sealed ends go on the filter and the other ends pushed into the supplied drain and return fittings also supplied. As these push fitted ends go into the tank you don't need to worry about drips. As we needed extra long hosing to get 1.5 m high we got away with the supplied as we didn't need any drain hosing.

So filters ready, pipes ready, drains and returns ready. Now to fill the 2500 litres which took almost 6hours due to the extremely low water pressure!

After 6 long hours we switched the FX6's on and as our drains where flooded they kicked in straight away! If we didn't have flooded drains and the pipes went up and over the tank then the FX6 are designed to purge themselves but in our case they worked immediately. After a few minutes both filters shut down to evacuate any trapped air. Ok we admit we got caught out and thought there was a problem only to remember this is a feature built into the FX6 so don't worry if this happens. This feature also happens every 24 hrs to evacuate any trapped air!
Then they automatically kicked back in and the first thing that struck us was just how silent they where! We was under the tank working on the lighting units and had our ears very close to the units but had to check they where in fact running as they where just so quiet!!!
As we had a 1.5m head height we was concerned the flow would be dramatically reduced but we shouldn't have worries. We climbed up to test the flow from the twin outlet adjustable flow pipes and they where belting out! A huge turnover of water.

Within a few hours our aquarium was crystal clear! All ready for fish!

Our verdict:

Another excellent filter from Fluval which hasn't let us down. There haven't been that many changes on the Fluval FX6 but when something is so good I think its hard to improve! The maintenance features although a handy feature could have been better but handy all the same! Even at such a high head head height these filters perform with a high flow rate. The filter media capacity is huge and its a truly robust beefy filter designed for big waste, big tanks. If your looking for a quality filter that will run and run without letting you down without too many technical gadgets then this is for you. There is more advanced technology such as Eheim e filters that you can rig up to your PC etc but none are built like the Fluval FX6.

High flow rate
High filter media capacity
Automatic purge feature
Smart pump technology with stop start feature to evacuate trapped air. Also helps keep the running ultra quiet
Very robust and solidly built
Drain port at base of filter handy for water changes
Maintenance reminder dials
Supplied with biomax media

Maintenance reminder dials could be better
No instructional DVD
Not many changes from the FX5 BUT we think its difficult to improve much on an already brilliant filter

Complete Aquatics score : 5 out of 5

Please click on the link below to buy a Fuval FX6 now!


  1. This comment has been removed by the author.

  2. A great review, which is unfortunately tainted by the fact that the authors' impressions are sometimes driven by insufficient understanding of the physics behind canister filter operation.

    When both ends of the tubing are submerged, then your canister filter is an example of so called "closed system" (see link below). In closed systems the height difference between the filter and the pump does not create any load on the pump at all. In more technical terms, in a closed system the static portion of pump head is always zero. For this reason, the flow in such system is completely insensitive to the height difference between the canister and the tank.

    (See here for technical details and terminology:

    You should not expect any reduction in the flow with 2 meter height difference, 5 meter height difference or 10 meter height difference. In a closed system this simply does not matter at all. (It is true that longer hoses will create more drag, thus reducing the flow somewhat, but this a different story.)

    For this reason, your excitement about "vertical" performance of this filter's pump is completely misguided and irrelevant. For canister filters this is simply not a factor at all. Things like that matter for open systems, like wet-dry filters, where the pump does indeed have to work against the static head created by height difference. But not in canister filters.

    The reason filter manufacturers mention recommended maximum height difference (which, I agree, should not be exceeded) is that grater height always leads to greater pressure inside the canister. The canister seals have their limits. If you exceed these limits, the canister will begin to leak. This is the one and only reason each canister filter has max height rating. It is about seals and only about seals, not about the pump power.

    1. Though Canister may be closed loop, but the tank is open to atmospheric pressure else where does the oxygen for the fishes/plants come from?
      May be I am wrong?

  3. Great review!
    I am only shocked by this ignorant comment made by Andrey Tarasevich. Your Sir should read the review and shut up if you don't have a clue of what you're talking about! A canister filter is never a closed system! NEVER! You should get back to school and learn some physics! The only way this could be a closed system was if the tank was completly full of water and completly sealed with no air or in a vacuum like state wich in an aquarium is impossible to achieve because you have to have air exchanges. Your affirmations reveal a profund ignorance about fluid dynamics! You underestimated the effect of atmospheric pressure, you know the "weight of air above us" wich has a very important role in this matter!
    So of course vertical heigh is important and a matter of decision when buyng a cannister filter and the more power the pump has the more height it can get the water back to the aquarium! That's how it works you dumb! It doesn't matter at all if the other end is submersed or not, it's almost exactly the same thing, it won't change the flow/power of the pump! Of course you cannot have this FX6 filter running 10 meters below an aquarium either you submerse the returning point or not. That is just a big LOL and anyone with more than one neurone can see that and you can test this on your own easily. The problem is not the drag on the hose, it's really the height. Go study some physics and then you can come back and make a constructive and relevant comment, not getting here to reveal a profound ignorance about the matter saying stuff any 16 yo kid can say otherwise and be right about it!

  4. .... GT .... Andrey in indeed correct, I am an expert in hydraulics, I make my living from hydroelectric systems repair and maintenance, a system can have both open and closed sections, the canister filter in this case is indeed a closed section. many closed sections can exit to an open section (tank) but prior to that they are still closed systems and his comments regards the flow rates as a result of head pressure are correct as well. If you have 1m of head flowing into the canister, and 1m flowing out then tyhe head is effectively 0m and flow rate will be only affected by drag in the system.

    1. I am not an expert, pls excuse me if I am wrong.
      How do you explain the atmospheric pressure acting on the main tank that will transfer to the canister?

  5. I have just bought 2 fx6 cannisters & they bought have problems with stopping & starting too evacuated the air why ? Done everything to instructions