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Fluval FX4 Canister Filter Review

To keep your aquatic pets healthy, changing the water regularly is very important. Aquarium maintenance is made easy if you have a canister filter that you can use.

If you don’t have one yet and you are looking for one, then this is a good read.

So let’s dive into our Fluval FX4 Canister Filter Review!

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What is an Aquarium Canister Filter?

For starters, a canister filter removes any existing water from a fish tank or aquarium. By using an intake tube, valve, or sieve, water runs through a filter media inside the pressurized canister. Then, the now-filtered water goes back to the aquarium via spray bars or spillways.

How does an Aquarium Canister Filter Work?

Using a lift tube, a canister filter draws water up and out of the aquarium. Then, it passes through an external filter canister where it gets ready for the filtration process.

Depending on which filter media you choose, a canister filter offers mechanical, biological, and chemical filtration.

Through a series of filter media, the existing water is cleaned before pushing it back in the aquarium. There are four possible directions where the filtered water can flow. These are top, top to bottom, back to front, outside-in, and center-out. However, these will depend on the brand of canister filter you’re using.

Fluval FX4 Canister Filter Review

With European ingenuity and innovation making it possible, here comes the newest member of Fluval’s FX Series. Featuring a SMART PUMP mechanism, FX4High Performance Aquarium Canister Filter combines efficiency and practicality with its uniquely sleek design.

Taking the excellence of its predecessors 406 and FX6 canister filters, this newest product from Fluval’s FX Series allows you to take care of both marine and freshwater animals with its 250-gallon capacity. With its multi-stage filters, it can pump out 700 US gallons (2650 liters) of water per hour.

Knowing that this product is proudly European, you are guaranteed with the clearest and cleanest water for your little buddies.

Advanced Microchip Technology

Due to its Smart Pump advanced microchip technology, it can continuously monitor and maximize pump performance. Since its Smart Pump does all the work, all you have to do is add water and plug the filter in. To ensure maximum efficiency, its trapped air is auto-evacuated every 12 hours.

With its 41.9 cm height, it can easily fit under most aquariums. Its removable and stackable media baskets can also remove water bypass and hold over 1 US gallon (3.9 liters) of media. From mechanical, biological, to chemical filter, all filter media are included upon purchase.

To remove the water, all you have to do is attach the hosing to the output. Then, it’s Smart Pump will do the rest. This will save you the hassle of lifting heavy buckets of water.

Albeit heavy-duty functions, the product remains to work with minimal noise. Not only this makes your aquatic pets undisturbed, but also allows you to work quietly while the filter does its thing.

While Fluval’s canister filters are some of the best units in the market today, no product is perfect.

Although many customers are greatly satisfied with the product, some had issues with how its installation process can be difficult. Some commented on how the clamps don’t fit with the trims; hence breaking them in the process. Also due to its automated mechanisms, it’s expected that this product falls on the pricier side.

However, many users didn’t mind splurging on this product that can stand the test of time.


  • 45-degree angled valves for easy installation
  • Anti-clog and telescope strainers for continuous water flow
  • Nozzles are multi-directional which makes them easily adjustable for better water flow
  • Perfect for saltwater and freshwater aquariums
  • Rubberized feet for quiet operations
  • Made in Italy


  • Biological Volume: 3.9 liters
  • Filter Circulation: 1700 liters per hour
  • Filtration Volume: 14 liters
  • Head Height: 2.1 meters
  • Mechanical Area (Foam): 1400 cubic centimeters
  • Power: 30 watts
  • Pump Output: 2650 liters per hour

Included Parts

Think that the canister filter is all you’ll get upon purchase? Here’s the good news – it inlucudes 13 freebies to get you started with your newest pet care provider:

  • 1.2 media basters
  • Drain cap
  • Filter canister
  • Filter lid and accessories
  • Intake stern
  • Lid fasteners
  • Media baskets
  • Output nozzle
  • Pump unit (motor) and power cord
  • Ribber hosing
  • Rim connectors, clips, and suction cups
  • Rubber feet
  • Utility valve and hosing

Pros and Cons


  • Easy Water Changing and Removal
  • Fast-operating
  • Self-starting
  • Sleek Design
  • Smart Operations
  • Quiet Operations
  • All Filter Media Included


  • Quite Expensive
  • Limited Filter Media Space
  • Difficult Installation
  • To give way for a compact design, its filter media space is rather limited.

Check Price and Reviews on Amazon

Video: “Fluval FX-4 Install for the 125 Gallon Overhaul! KGTropicals!!”

Fluval FX4 Review: Frequently Asked Questions

Have some questions in mind? Look for similar answers in our Frequently Asked Questions (FAQs) below:

Can you connect an inline heater model to the filter?

No. Since the canisters are made of ribbed flexible nosing, installing such equipment would be hazardous.

Why is it difficult to restart the canister filter after cleaning it?

With this, there are three possible causes you must look for. First, check if your impeller and impeller shaft is dirty. If yes, clean them out and check if your impeller cover is perfectly attached. If not, reattach them properly. Lastly, check if the filter is correctly primed above the water surface.

You’ve noticed your canister filter to perform poorly. Are you doing something wrong?

No, you’re not doing something wrong. This is mainly because of increased loads in your filter caused by more fishes, increased waste production, or clogged filter media.

Should you be worried if you’ve seen bursts of air coming out of your filter output?

Although this problem isn’t entirely serious, opt to install a bubble trap for your skimmer to avoid this issue.

How does your house’s ceiling height affect your filter’s performance?

Since the canister filters are closed recirculation systems, your house’s head height doesn’t affect their performance. However, make sure to follow the recommended vertical distances to make sure your aquarium will get the best filter operations.

Is it too often to change your carbon filter every two weeks?

No, it’s better to replace your carbon filter often. This is especially true for aquariums housing many messy fishes.

Is the flow too strong if you’ve found a fish stuck in your filter’s intake?

Since fish can easily swim even in stronger ocean currents, this isn’t something you have to be concerned with. If a fish was stuck in the filter, there’s a high chance that it’s too sick to swim properly.

However, you can also adjust your filter output strength to match your fishes’ health conditions.

Do you need additional filters other than those that came with the product?

For long-term performance, you might also consider adding a coarse pre-filter media at the bottom of your canister filter.

If you’re keeping extremely messy fish, what filters should you combine?

For messy species with strong eating and digging tendencies, we recommend using the Fluval Fine-Filter pad and chemical media like carbon at the bottom of the aquarium.

In the middle level, you can add Fluval Bio-Max while Fluval Pre-filter rings work perfectly at the top.

There’s a slight rumbling noise in your canister motor. Should you be concerned?

When this happens, it’s a sign that your impeller assembly must be replaced. However, this is entirely normal due to impeller’s wear-and-tear properties. Upon replacement, make sure that the filter is perfectly primed above the water surface.

Why is your canister filter emitting fine air bubbles inside the aquarium?

For freshwater aquariums, this is typically caused by air accumulation. This is why performing regular filter maintenance is a must.

For saltwater aquariums, this is usually caused by protein skimmers introducing fine air bubbles into your canister’s filters. To avoid this, you can use a bubble trap at the skimmer output or along with the sump.

How can you reduce the flow of your filters using the Aquastop valves?

For safety purposes, you can only reduce the flow speed by 50%. Doing so is the safest way to avoid any filter pump damage.

What should you do if there’s a small leakage from your canister’s handle?

This issue is caused by a faulty canister O-Ring. Before installing the replacement, make sure to carefully clean and remove it with warm water.

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As you can see from our Fluval FX4 Canister Filter Review the FX4 focuses on efficiency and practicality. It got nothing but praises when it comes to effectiveness and longevity.

Aside from its long-lasting properties, a customer also commented on how the filtered water stays remarkably clear after several days. Since the product is well-made, little to no replacements have been recorded based on Amazon reviews.

Interested to purchase one for your pet?

Check Price and Reviews on Amazon


Aaron Boyd
Aaron Boyd

Hello, I’m Aaron Boyd, the proud owner and author behind Aqua Movement. I hope my article was able to answer your questions. If you want to learn more about me, click the home icon above.

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