How Does A Canister Filter Work? And What Are The Best Choices

There are several types of aquarium filters or filtration systems on the market. They include canister filters, diatom filters, trickle filters, algae filters, baffle filters, airlift filters, and under-gravel filters.  

All aquarium filters and filtration systems serve one purpose – they remove chemicals, biological waste, and other materials from fish tanks. While all aquarium filters do the same thing, they are different from each other. They filter aquarium water in different ways and they all have their pros and cons. 

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Canister filters are very popular among aquarists in the United States and in the United Kingdom. They are popular because they are very effective aquarium filters.

By definition, an aquarium filter is an external filter in the form of a pressurized canister (cylinder) that is packed with filter material. It uses a pump to draw aquarium water and push it through the filter material to clean it before returning it to the aquarium via an outlet. Its main parts are the canister, the filter material inside it, the pump, and the connecting tubes/ pipes. 

Canister filters are better than most other types of aquarium filters because they do not take up space in the fish tank. They are external pumps. This means they allow you to have more water in your tank and more space for your fish to swim. And since canister filters are external, it also means that cleaning them does not stress aquarium inhabitants since it is done away from them. 

So if you are looking for an aquarium filter that is powerful, effective, and does not take space in the fish tank, you should strongly consider getting a canister filter. Remember, you cannot do without a filter especially if you are keeping a messy fish e.g. a goldfish, a cichlid, or an Oscar fish. 

How Do Canister Filters Work?

Generally, canister filters work by drawing aquarium water into their pressurized canisters and pushing the water through the filter material packed in the canisters to clean it. And when the water is cleaned it exits the canisters via an outlet and gets directed back into the fish tank. Different brands and models of canister filters work in slightly different ways but the mode of operation is still the same as explained above. 

Most canister filters have filter media that provide biological, mechanical, and chemical filtration. Some filters can with the filter material, while some don’t. You have to buy the material separately. 

Most canister filters have inbuilt pumps to move aquarium water. However, some do not have inbuilt pumps (you can buy a compatible pump separately). 

Maintaining canister filters is generally much easier than maintaining other types of aquarium filters since they are external filters. 

The 8 Best Canister Filters For Aquariums

Now that you know basic detail you need to know about canister filters, it is time to discover the eight best canister filters and their pros and cons. Without further ado, here they are:

  1. Fluval External Filter

This is one of the best-rated canister filters available on the market! It features cutting edge technology and it is available in various GPH sizes for different fish tank sizes. 

The best thing about this filter is its technology. It features a strong and tough motor for moving aquarium water and has a special protective material to reduce the noise it makes. 

All Fluval External filters (for the different tank sizes) use their entire canisters to do filtration work and are very efficient. The filter media packed inside them is capable of absorbing all kinds of waste and chemicals. 

The one thing you may not like about this filter is the fact that it is a bit pricey. 



  • It comes with a powerful motor 


  • It works quietly 
  • It features a multi-stage filtration system
  • It comes with filter media
  • It is easy to maintain 
  • It has a three-year warranty 





  • It is a bit pricey


Despite being a bit pricey, this Fluval canister filter is definitely worth the money. This is because it is efficient and very durable. 

  1. SUNSUN Pro Canister filter

This is also a highly-rated canister filter. It is powerful and it is available in a variety of GPH sizes from 264 to 525. 

The thing that stands out the most about this filter is the fact that it is a very powerful biological, chemical, and mechanical filter. It produces very clear water and it works very fast. 

Unlike other canister filters, this filter also comes with a UV sterilizer. The sterilizer kills bacteria and algae and removes chlorine and chloramine from water. In other words, this filter will make your aquarium water as healthy as it can be for your fish. 

This SUNSUN filter is a breeze to clean and maintain.

The one thing you may not like about it this SUNSUN filter is that its UV sterilizer is not very durable especially if used very frequently. 


  • It is a three-stage canister filter system 
  • It is available in various GPH sizes
  • It is almost noiseless
  • It comes with a UV sterilizer to kill bacteria 
  • It primes itself and comes with filter media


  • Its UV sterilize is not very stable 

Although frequent use of this filter’s sterilizer will reduce its lifespan, the filter itself is very decent and it works like a charm. 

  1. EHEIM Classic External Canister Filter

This EHEIM filter features German technology and it is very efficient. It has been on the market for quite some time now and it is very popular. It has continued to sell for so long because of its simplicity and efficiency. 

The filter is available in various GPH sizes for 90, 66, and 40-gallon tanks. It comes with its own media and it is designed in such a way that all aquarium water must pass through the media. This ensures aquarium water is thoroughly cleaned. 

If you buy it you will like how compact it is and the fact that it does not make much noise. You, however, won’t like that it is not very easy to clean. 


  • It is a relatively cheap but efficient canister filter
  • It is available in various GPH sizes and comes with its own filter media
  • It is compact and almost noise-free


  • It is not the easiest to clean 

While this canister filter is not the easiest to clean, it is cheap, efficient, and durable. So it is definitely worth going for especially because you won’t need to clean it frequently.

  1. Fluval FX6 External Canister Filter, FX6 Filter (400 Gal)

On Amazon, more than six hundred people have given this machine an average rating of 4.4 out of 5 stars. This shows just how good this machine is! 

According to Amazon reviews, the thing that most people like about it is the fact that it is a very powerful filter with six filtration stages. In other words, they like that it cleans water six times before releasing it back into a fish tank. 

People also like the fact that it has a great filter media that ensure no debris or chemical waste escape each filtration round. 

Many people also like that it is a smart filter that is self-priming. 

What most people don’t like about it is its cost but they all say that it is worth every cent of its cost price. 



  • It is a highly rated canister filter


  • It has six filtration stages in each filtration round
  • It has got great media that filters really well
  • It is smart and durable 
  • It is super quiet 
  • It is recommended for aquariums up to 400 gallons




  • It is very pricey

Despite being expensive, this is a powerful canister filter that can be used to clean medium-size and big-size fish tanks. 

  1. Penn Plax Cascade Canister Aquarium Filter

This is one of the most popular external canister filters on the market! It is mainly popular for one reason – it is a heavy-duty filter multi-stage filter that is capable of quickly turning hazy aquarium water into sparkling clean and healthy water.

It is quite easy to install compared to many similar filters because it comes with everything needed (except filter media). And it can be used for either freshwater or saltwater fish tanks. 


  • It is a heavy-duty and long-lasting filter
  • It is very quiet 
  • It comes with a handle


  • It does not come with filter media/ material 

While you won’t like that it does not come with filter media, you will probably love how clean and healthy it makes your aquarium water. You will also love its durability.

  1. Hydor Professional External Canister Filter

Hydor is a renowned maker of aquarium components. They make very good pumps and external filters. This external canister filter is one of their best products yet!

It is an efficient external canister filter available in various GPH sizes from 160 to 290. 

The most exciting thing about it is that it is easy to install. It is also very convenient to use. 

It is called a professional filter because it is powerful, it does the job, and it is very durable. It is also very quiet for a powerful canister filter.

I like that it is a multi-stage filter like most Hydro filters. But you won’t like the fact that its replacement parts are difficult to find because it is a new filter. 


  • It is a quiet but powerful canister filter
  • It works really well
  • It is easy to install and run
  • It has an expendable sprayer


  • Its replacement parts are difficult to find
  1. Aquatop CF Series Canister Filter

Equally effective in clearing waste, debris, and chemicals from both saltwater and freshwater tanks, this AquaTop canister filter is a great machine to have.

It comes in three sizes and its biggest size can clean a 175-gallon tank. 

Like the highly-rated SUNSUN Pro Canister Filter reviewed earlier, this filter also comes with UV sterilizer. The sterilizer clears the water of parasites and harmful algae. So this canister clears everything from aquarium water and returns super clean water.

It comes with everything needed to install it including filter media that includes powerful activated carbon.

The only thing you may not like about it is that it is relatively expensive.


  • It is a great canister filter available in various sizes
  • It has an adjustable intake pipe
  • It features a UV sterilizer
  • It is easy to prime
  • It comes with its own filter media including activated charcoal


  • It is expensive 
  • Its spray bar is not the easiest to install

This filter might be expensive. It might also not be easy to install. However, it is one of the best external canister filters as it cleans fish tank water really well.

  1. Marineland Magniflow Canister Filter for Aquariums

This filter comes from a renowned manufacturer of aquarium filters and it is a great unit especially for small tanks below 100 gallons. 

It is an affordable 3-stage filtration system machine that is capable of cleaning both freshwater and saltwater aquariums. 

It comes with filter media that provide biological, mechanical, and chemical filtration. It also has special carbon material that eliminates discoloration and odors. 

The one thing that is not amazing about it is that it gets air bubbles when it starts.


  • It is a cheap canister filter
  • It is easy to set up
  • It has great filtration media
  • It is well-made and durable


  • It gets air bubbles when it starts

This is a great machine that you will love to own as it works brilliantly. 


As you can see above, there are quite a number of great canister filters on the market. They are all capable of providing great filtration and making aquarium water clean and healthy. The best one, in my opinion, is the AquaTop filter since it is efficient and it also comes with a UV sterilizer. The Penn Plax Cascade Canister Aquarium Filter is also a really good option.