Fluval Fx4 Review – Detailed Testing, Review, Guide, FAQs & More

If you’ve been a fishkeeper for some time, you’ll agree with us when we say that Fluval is one of the most reputable brands out there when it comes to aquarium equipment. 

Owing to this, we decided to put their FX4 filter to the test in order to find out if the hype was justified or if it’s all just a sham. 

Today, we’ll look at every aspect of the Fluval FX4 filter in detail, explore what makes it tick and discuss whether it’s worth it for you or not. 

Fluval Fx4 Review

Coming with an incredibly robust body, this product provides you with something that will last for years. Despite its bulky appearance, it’s very easy to handle and works extremely quietly.

Alternate #1

This product is for fishkeepers looking for effective cleaning on a budget. It has a very impressive flow rate and an attractive design.

Alternate #2

Coming with a number of different types of accessories and filter media, this product provides you with everything you need to mix and match.

Quick Summary of the Main Product

Fluval made huge waves in the fishkeeping community when it came out with the FX5 filter model; it was affordable, easy to use and effective. Then came the newer FX6 to replace it with its jet-black body and high flow rate. It quickly became known for its effective filtration coupled with its ease of use and silent mode of operation. Now, the insanely popular Fluval FX6 filter has a smaller version: the Fluval FX4 filter. 

The Fluval FX4 is rated to be appropriate for tanks up to 220 gallons. It has an impressive pump output rate of up to 700 gallons per hour with a filter circulation rate of 450 gallons per hour. Even with numbers this high, the Fluval FX4 filter only takes up 30 watts of power. It’s an incredible option for fishkeepers who are energy-conscious. 

With a built-in smart pump that constantly optimizes pump performance coupled with a streamlined, easy-to-handle design, the Fluval FX4 is extremely user-friendly. You’ll find that you’ll have this filter up and running in no time both when you first set it up as well as after cleaning and maintenance sessions.

Features and Benefits

  • Filter Media – Fluval Fx4 Review

The extra space that the Fluval FX4 provides for filter media is a very welcome and useful feature. 

You have the three main stages of filtration: at the top, you’ll find the media for mechanical filtration which filters out large particles from the water such as debris and waste. After that comes biological filtration which neutralizes harmful bacteria in the water and at the end comes chemical filtration which eliminates harmful chemicals in the water. 

Even after these three media, you’ll notice that there’s still more space inside the filtration basket for more filtration media that you can add. What type of filtration media you want to add is really up to you. We would recommend an ammonia remover or even a water polisher.

  • Self-Primer

What happens if you don’t prime your filter? It can lead to a number of consequences such as the motor of your filter burning out very quickly. Thus, priming a filter is a tedious process that can’t be skipped. It has to be done every time after cleaning and maintenance of a filter and can take a lot of time and effort. 

The fact that the Fluval FX4 filter is self-priming really makes it stand out from the crowd. It decreases the amount of work you have to get it running by a lot. 

All you have to do is mount the filter to your aquarium, fill it up with water and turn it on. No need to do any of the silly actions such as tilting it sideways and then moving it upwards that other common filters require you to do during priming. 

The smart pump technology that’s built into it readjusts the pump every 12 hours so that the performance of your filter stays optimized and it keeps filtering your aquarium at the most appropriate and efficient rate. 

If you don’t have experience with self-priming filters before then we must warn you, when a filter is readjusting itself, it can be quite loud. It may take some time for you to get used to it but just know that the loud noise is normal and it only lasts for 1-2 minutes when it happens. 

  • Utility Valve

The utility valve that’s built into it is also a very convenient feature that can save you a lot of time. It can be used to attach a gravel cleaner to it so you can easily vacuum clean your aquarium’s gravel and at the same time, it also makes it super simple to perform water changes. 

This means that when you have to make a large water change or empty your aquarium of water entirely, you don’t need to chug buckets of water around. All you have to do is attach a hose to the utility valve and take the other end of the hose out to whatever place you want to dump your water such as your backyard. 

While you can definitely utilize the filter to fill up your aquarium as well, you have to be wary of the fact that the water needs to be treated before you can fill your aquarium up, i.e., the water needs to be dechlorinated and treated with a water conditioning agent. If you don’t do this and simply add regular tap water to your aquarium using your Fluval FX4 filter, it will kill all the beneficial nitrifying bacteria inside the filter as well as in your aquarium. 

  • Anti-Clog Strainer

Filters can often get very frustrating to clean when they get clogged. This is because the sort of sludge that gets deposited that eventually forms clogs is often very sticky and difficult to get rid of. This is where the handy dandy anti-clog strainer comes in. 

It’s incredibly versatile with the types of materials it’s able to take out of your filter and you’ll find that it’s incredibly easy to use. It takes little to no effort to pull all the gunk and debris out of your filter that would be blocking the filtration path. 

  • Rubberized feet

The rubberized feet are a part of the ingenuity of this product’s elegant design. Not only they do look great but also unassuming, they also provide a lot of functionality. 

Firstly, they ensure that the filter is firmly held in place during its operation as well as during readjusting and self-priming procedures. 

Secondly, you’ll find that they play a huge role in making sure the filter operates silently. You don’t want big, plastic or metal feet to constantly be whirring and making a lot of noise on a filter. That’s why these feet are absolutely perfect for ensuring the filter runs in a way so that it doesn’t disturb you or your precious fish.

  • Leak-Proof Valves

You’ll be pleased to know that all the valves and tubing that comes with the Fluval FX4 filter and the ones that are built into it have all been reinforced to ensure no leakage of any kind ever occurs within the filter. 

Pros and Cons

  • Owing to the lift-lock clamps as well as the removable and stackable buckets it comes with, the Fluval FX4 filter is incredibly easy to install and mount onto aquariums of many different shapes and sizes. 
  • With its smart pump technology as well as self-priming capabilities, the Fluval FX4 filter is very easy to operate. Once it’s mounted, it takes a minimal amount of effort from you to get it to start running. Just fill it with water from your aquarium, turn it on and the smart pump does all the rest. 
  • The inside of the filter is designed in a very clever way which ensures that a majority of the waste that is filtered out does not get stuck or clogged within the confines of the filter. This is important as it prolongs the periods in between cleanings. The Fluval FX4 filter needs to be cleaned almost half as times less than most of its competitors. 
  • It has a flow rate that is unmatched by most of its competitors of a similar size. Not only is the flow rate powerful, but it’s also adjustable so you can precisely control how much water you need to filter every hour according to the size of your tank and its inhabitants. 
  • When you look at the Fluval FX4 filter, it looks quite heavy-duty and bulky and from that appearance, you would think that it would be a very noisy piece of equipment but we’re here to tell you that the truth is quite the opposite. As we discussed above, its rubberized feet play a huge role in dampening the noise and causing the filter to operate very silently. 
  • While the Fluval FX4 filter is definitely jam-packed with convenient features, these features do come with a price. A price that could be very expensive and unaffordable for many fishkeepers. 
  • The Fluval FX4 filter is quite bulky and you may tire yourself out when carrying it to your aquarium. 

Social Proof

We scoured the internet for reviews of the Fluval FX4 filter in order to get an idea of what the experience of using this filter has been like for regular customers. Overall, we found the reviews to be overwhelmingly positive with only about 5 – 10% of the reviews being critical of the product. 

The general perception of most customers is that the filter is incredibly remarkable in its performance and delivers on all fronts that it promises. Most customers also agree that while its price point is fairly high, the amount of features it comes packed with definitely justifies it to some extent.

More Recommendations!

1. Budget-Friendly Alternative to Fluval FX4 - SunSun Hw304B 525GPH Pro Canister Filter Kit Review


The SunSun Pro Canister Filter Kit is a package that really gives you everything you need for running an efficient filter. The number of accessories that come in addition to the filter itself is very surprising. This includes a UV Bulb, 4 white filter pads, 1 blue coarse pad, and 4 different filter media baskets. 

The UV Bulb is a welcome addition which makes it stand out from other filters as the UV light allows you to eliminate any algae that might be developing inside your aquarium and keep it crystal clear.

Features of SunSun Hw304B 525GPH Pro Canister Filter Kit

  1. Appropriate for aquariums up to 150 gallons
  2. Flow rate: 525 gallons per hour
  3. Dimensions: 11 inches by 11 inches by 17 inches
  4. Comes with a UV Bulb
  5. Comes with filtration media and a number of different accessories
  • Combats algae in addition to filtering water
  • Attractive appearance
  • Easy to install
  • Easy to use
  • Affordable
  • Even heavier than the Fluval FX4

If you’re looking for a filter that has a similar performance to that of the Fluval FX4 filter but don’t have that much money to spend, this is the product for you. It’s much cheaper than the Fluval FX4 but it does not compromise on quality or performance.

2. Alternative for Smaller Tank to Fluval FX4 - EHEIM Classic External Canister Filter Review

The Fluval FX4 is definitely a beast of a filter but a drawback of that is that it’s not suitable for fishkeepers with smaller tanks. Having a filter as big as the FX4 in a smaller tank would lead to currents that would be too violent for the inhabitants. This product is the perfect alternative as it offers similar performance to that of the Fluval FX4 at a much smaller scale. 

Not only that, since it’s meant for smaller tanks, this filter itself also has a much smaller footprint compared to the Fluval FX4 and thus, is much easier to carry around and handle. 

Features of EHEIM Classic External Canister Filter

  1. Available in 3 sizes: for 40-gallon tanks, for 66-gallon tanks and for 92-gallon tanks
  2. Comes with filter media
  3. Spray bar and inlet pipe included
  4. Flow rate: 164 gallons per hour
  5. Suitable for both freshwater and saltwater environments
  • Easy to install
  • Easy to clean
  • Lightweight
  • Compact
  • Inexpensive
  • Slightly flimsy construction 
  • Ugly appearance

If you’re charmed by the incredible performance that the Fluval FX4 filter offers but don’t have an aquarium that’s big enough for it, this is the product you’re looking for. It does not take up too much space and is perfect for smaller aquariums.

fluval fx4 review

Guide to Buy

Before you go out and buy a filter for your aquarium, you should think about some aspects that pertain to an aquarium filter. These aspects will help you narrow down your search and decide what filter would be best for you. Some things to think about are: 

  • Build Quality

Obviously, you want a filter that is well-built and will not break down within a few weeks or months after you buy it. While purchasing a filter, be sure to look at its online reviews in order to ensure it does not have a bad reputation of breaking down or not working properly sometime after purchase. 

  • Price

Fishkeeping can be an expensive hobby and it’s wise to cut corners where you can. While we do advise that you think about your budget and invest in a filter that fits that budget, we also need to stress that you should never opt for a generic or cheaply-made filter as this could do more harm than good. 

  • Aquarium Size

Your aquarium size is very important when considering which filter you buy. If you buy a filter that’s too small for your aquarium, it will be inadequate and your aquarium will remain dirty and unhealthy for your fish. If you buy one that’s too big, the currents that it will create will be too much for your fish. It will stress them out and your fish might even get swept into the filter if it’s too strong.

Wrapping Things Up…

In conclusion, the Fluval FX4 filter is definitely a worthy investment that will stand the test of time. It offers incredible performance that will remain consistent throughout the years along with a design that aims to make life for the user as easy as possible. If you can monetarily afford to have this filter attached to your aquarium, we definitely recommend that you do as it has a ton of features that no other filter on the market provides.

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