Fluval C Series – Review + Opinions

When it comes to aquarium hobby, one of the most important pieces of equipment is the filter. No matter what fish or plants you have, the filter is vital to maintaining a healthy aquarium and always clean and chemically balanced water.

Because of the importance of filtration in an aquarium, having a good filter, in addition to having a healthier tank, means you won’t have to change the water too often or continually worry about variations in water parameters.

There are different types of fish tank filters to choose from, and when you start out in the aquarium hobby, it can be overwhelming trying to get the one that best suits your tank’s needs.

In this sense, one of the filtration devices that is worth considering is the fluval C Series cascade filter. . If you are looking for one of the best waterfall filters, look no further without first stopping by this review of the fluval C filter.

Fluval C Series Cascade Filters

The Fluval C Series range is a line of high quality aquarium waterfall filters. And while they are similar in some respects to the AquaClear line of filters, the C-Series filters offer some improved features and greater ease of use.

Thanks to its multiple filtration stages and a modular media compartment design, the fluval C filter keeps the water clear and makes it easy to clean and change media.

The water goes through five different stages of filtration, removing debris and harmful chemicals before returning the water to the tank.

The price is not too high and the filtration capacity is as effective or more than any of the best waterfall filters on the market.

If you want to have a great filtration system without the hassle of external filters, then the Fluval C-Series may be the ideal solution for you.


It has a modular filter media compartment design that allows you to change or clean only a specific part if necessary. It also makes it easy to custom configure your own media.

It features a 5-stage filtration system that does a great job at sifting out particles and filtering out impurities. These stages are two mechanical, one chemical and two biological.

This filter also features precise flow control with its patented Refiltration system, which allows you to adjust the flow rate without affecting the efficiency of the filter.

If the flow is decreased, up to 50% of the water in the filter is returned through the system, further filtering it and improving water clarity.

The Fluval C series is made up of 3 models of different sizes:

  • Fluval C4 for tanks from 150 to 265 litres.
  • Fluval C3 for aquariums from 75 to 190 litres.
  • Fluval C2 for fish tanks from 38 to 115 litres.

Technical data of Fluval C filters

The following video reviews all the features and benefits of the C Series fluval filter:

Fluval C2

Fluval C3

Fluval C4

Fluval C Cascade Filter Features

Key features of the Fluval C Cascade Filter are its 5-stage filtration system, cleanliness indicator and flow adjustment switch.

It also highlights its compact design, as well as the low noise level it produces when it is in operation.

Five stages of filtration

The five-stage filtration system passes the tank water through a cycle of mechanical, chemical, and biological filtration:

  • Stages 1 and 2: Mechanical filtration is carried out through a double-sided foam/polyester sponge. The porous side of the foam traps larger particles, while the dense side of the polyethylene foam filters out fine debris.
  • Stage 3: Activated carbon chemical filtration removes odors, impurities and discoloration. If you prefer not to use activated carbon, you can substitute another sponge or other material of your choice.
  • Stage 4: Mechanical filtration through the Bio Screen at the top of the drip chamber. This filters out any debris before the water drips into the biochamber, and ensures that the flow of water is evenly spaced.
  • Stage 5: Biological filtration with C-nodes. The unique “star shape” and porous surface of the C-nodes provide an optimal environment for friendly bacteria to live, enhancing ammonia and nitrate removal.

There is very little dead space inside the filter, so the water has to pass through the filter media. Everything fits together perfectly and the plastic components are of high quality and durable.

This five stage filtration works amazingly well. It keeps the tank water crystal clear, and the high flow rate ensures that all the water is passed several times per hour.

There is also an integrated cleaning regulator, which we will talk about next, which warns when the filter sponges become saturated and it is time to clean.

Speaking of cleanliness, the modular compartments make disassembly of this filter really easy, although there are a few nooks and crannies around the impeller that need special attention.

cleaning indicator

The saturation indicator feature may be more important than it seems.

No matter how hard you try to keep your Fluval C clean, it will periodically become clogged and become clogged with plant debris or fish debris.

You may not notice it from the outside, but the water in your tank will get dirty and toxins will spread everywhere. A simple visual indicator will keep this problem under control.

If the indicator is visible, remove the filter and check each media to find the clog. Then just wipe it off and put it back on.

Adjustable flow and filtration system

If you want your fish to spawn or delicate plants to grow, you’ll need a smoother flow of water that won’t get in the way.

To do this, Fluval C uses its patented refiltration system that allows the water flow to be adjusted without compromising the effectiveness of the filtering system itself.

When the water flow is reduced, the refiltration system causes the water to be reprocessed multiple times, further purifying the water.

The Fluval C flow rate adjustment switch is a simple three position switch. It works in low, medium and high power.

The high position moves the most liters per hour, but the low and medium settings will filter the water more effectively than the high setting.

Ideally, run the filter on a low setting when first starting up, allowing the filter to fill completely with water before running it on high power.

This prevents wear on the impeller that occurs when the motor runs at full power without water.

In addition, it is also recommended to use a reduced flow when feeding fish in order to make feeding more efficient and produce less waste.

Compact size

The compact design of this cascade filter series offers a really small filtration device, which is appreciated. No one wants a huge device that takes up as much space as the tank.

However, don’t be fooled by the small size of the Fluval C, as despite its compact size it is highly effective at filtering out all the dirt in the aquarium.

a silent filter

When it comes to aquariums of a certain size, the equipment is not only unsightly, but also often noisy. This means that placing the tank in the bedroom or in a quiet room can be a problem.

The filter is the device that makes most of the noise. However, the Fluval C this will not be a problem

Due to its compact nature, the parts are connected in such a way that no disturbing noise is heard when the filter is on.

Start up

This filter is very simple, and it is not very difficult to get it to work, however, Fluval recommends that you familiarize yourself with and understand how this filtering device works.

The ideal is to disassemble the filter to know the different parts, and check that they are all in good condition.

What must be done before putting it into operation is to rinse the different filter materials to eliminate any residue that may have been generated.

After cleaning the media, the suction tube must be assembled, the filter charges placed, placed in the tank and the leveling device adjusted for optimum performance.

Now you have to fill it with water, adjust the flow lever to a minimum flow and plug in the device. You will have to wait a few seconds for the filter to prime itself and expel any air that may remain inside.


Fluval has made a video where you can easily see how to open the filter and clean any of the components.

First you have to unplug the filter. If the filter has not been used yet, it can be disassembled directly. However, if you’ve already been using it, you’ll need to drain the filter or place it in the sink before you start disassembling it.

To access the filter components, simply remove the filter cover. There are multiple handles to remove components in specific ways, each sliding or snapping into place.

The filter foams, located in the red basket, can be reused several times after being rinsed well. Always remember to use water from the aquarium itself, never from the tap, otherwise you will kill the beneficial bacteria. For best results, it is recommended to replace them every 1-2 months.

The biological C-Nodes, located in the upper basket, which house most of the beneficial bacteria, just need to be rinsed a little with aquarium water. Never with tap water, as the chemicals would kill the colony. Also, make sure they don’t stay dry for too long.

Half of the C-nodes can be replaced every 6 months, but never replace all at once, or you too will run out of nitrifying bacteria colony.

The motor is released simply by turning and then pulling down, using little force. The motor uses a magnetic rotor, which can be removed for cleaning.

You can use a specific brush or a cotton swab to clean it, carefully, as it is a delicate piece. Any scratch will cause irregular rotation, which will weaken the flow rate or damage the impeller.

When you’re done, put the impeller back in place.

Warranty and shelf life

This also applies to your guarantee. The Fluval C Series backpack filter comes with a two-year warranty.

The average life of this filter is 4-5 years. The only component that can break is the impeller, so treat it carefully and keep it clean.

If you are using the filter in a tank with long, stringy plants, you may need to clean the motor more often to prevent damage.

To get the most out of your filter, we suggest you have it inspected thoroughly when your warranty expires. Look for any damage and if there is, contact Fluval. We know that they can help you if something has degraded too much.

Advantages and disadvantages of the Fluval C


  • 5 stage filtration system
  • It is a waterfall filter that works as an external filter
  • Large capacity for filter media
  • Possibility of customizing filter loads
  • Modular compartments make it easy to disassemble and clean
  • Adjustable water flow


  • Double-sided foam sponge needs to be replaced every few months
  • System dripping water onto bio-media can be prone to clogging
  • Impeller cleaning can be a bit difficult

Opinions about the fluval C Series filter

In we do not find many customer reviews, just over 30 at the time of writing this post. The average rating for these filters is 4.3 out of 5, a remarkable high.

70% of reviews have given these waterfall filters 5 stars. 7% have rated with 4 stars, and 14% with three stars. The remaining 9% have given it 1 star.

If you click on the above link and look at the bottom of the page, you will see a link to where you will find almost 900 reviews. In this case the grade is 3.6 out of five.

60% have rated this filter with 5 stars, and 12% with 4 stars. This represents more than 70% of the opinions, which is not bad at all. The rest is divided into 8% with 3 stars, 8% with 2 stars and 12% with 1 star.

Most people value this filter very positively, its great capacity for filter media, its efficiency, its ease of cleaning…

And among the negative opinions, several comment that it has to be cleaned too often, and another client complains that it makes too much noise.

Other alternatives

Conclusions about the fluval filter C

All of its features provide aquarists with the opportunity to upgrade their tank with a product that provides multiple stages of filtration, quietness, compactness and much more.

Fluval C is a waterfall filter with a five-stage filtration system that works very well, and is easy to use and easy to clean. It is also very easy to install and remove.

The Fluval C – Series is a step up from Hagen ‘s excellent AquaClear line of filters, which Fluval also owns.

With this filtration device you can be sure that you are buying an efficient and durable filter to have crystal clear and healthy water in your aquarium.

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