Best Filters 20 Gallon Aquariums: 2020 Updated

Get straight to the point! What to expect from the best filters 20 gallon aquariums?

In brief, recommended filters should be either hang-on-back (HOB) filters, the internal filters, or the canister filters. They must also be compatible with the capacity, as well as the design, of the tank and also with your room space.

Moreover, get to know your fish. Do they prefer natural and quiet habitat? Then, you had better use filter with a strong, yet silent, outflow.

Keep reading to figure out more information.

What Type of Filters to Choose for a 20 Gallon Aquarium?

 In fact, there are many types of filters on the market. However, we only recommend three types as above for a 20-gallon aquarium, including hang-on-back (HOB) filters, the internal filters, and the canister filters.

HOB filters

HOB filters, as known as the power filters, are often built to mount on the side or the back of the tank. However, some small designs are even interiorly placeable.

On operation, the intake tubes of the filters are put into the water to compel the flow into the media box. There, the water is carefully filtered before being sent back to the fish tank through a return/spillway tube.

HOB filters are the easiest to use and maintain thanks to their remade placement filters. Moreover, they also come with many advanced, adjustable, and adaptable parts.

In drawbacks, some HOB filters are pretty loud. Not to mention, the intake tube might not be safe for very small fish.

Internal filters

Unlike the external accessories like HOB filters, the internal filters – as the name might suggest, are submersible placed inside the aquarium.

First off, you can save much room and even hang your tank up against a wall.

Secondly, these filters are strongly recommended for small fish tanks because they can handle dead spots better than in large tanks. More importantly, they support additional filtering because of the very high bioload included.

Thirdly, the internal filters are small, quiet, and easy to set up.

Canister filters

Another choice for best filters 20 gallon fish tanks is the canister filters. This type of filter works well for saltwater or planted fish tanks, as well as the freshwater tanks.

Canister filters are mounted outside of the aquarium with hoses submerged in the water to filter the unwanted substances. The filtration is exceptionally helpful and powerful.

However, canister filters often do not go cheap. Neither are they easy to set up and maintain. For that reason, they are not a good choice for beginners.

Choosing a Filter for 20 Gallon Aquarium

Besides you decide what types of filters for 20-gallon aquariums, you should consider the following factors.

Know your fish first

Many people might miss this point!

They search for the incredible filters which can get rid of almost all waste from the tank. However, you should learn that many fish like a natural habitat. Also, some picky fish do prefer some specific sorts of chemicals.

Thus, you should not filter out every piece of dirt or the like.

The filtration technology

The next step is to consider what the filter can do with your fish tank. There are three technologies commonly found in the best filters for 20-gallon aquariums.


  • Mechanical filtration: In this stage, the filter helps remove debris and floating particles by filtering them through various media.
  • Chemical filtration: It is in place to get rid of harmful or unwanted substances that can affect the quality of water. To fasten this process and lengthen the lifespan of the filter, we recommend treating water in advance.
  • Biological filtration: Finally, do not ignore the micro-life and toxic byproducts inside the tank. They can be good or bad for your fish. Naturally, the biological filtration encourages the harboring of beneficial bacteria by breaking ammonia down into nitrates. You can choose the best biological filter media here.


The water-flow rate

This figure is visibly shown in specifications. It refers to the gallons per hour. The higher rate means that the filter can fill the aquarium faster. However, it can also mean a noisier filtration.

Ease of installation and maintenance

Earlier in this post, we have revealed three types of filters. The HOB is by far the easiest to install. The internal filter comes after and the canister filter is quite tricky to install.

In addition, you need to clean or even replace some parts of filters after a while to maintain their capacity. Thus, also consider whether you can maintain the filters yourselves or you need to spend an extra to have the professionals do it for you.

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Best Filters for 20 Gallon Aquariums

Product Images Product Name Editor's Rating Prices
AquaClear - Fish Tank Filter 4.2 out of 5 stars (4.2 / 5) See price on Amazon
Tetra Whisper Power Filter for Aquariums 3.9 out of 5 stars (3.9 / 5) See price on Amazon
Fluval C3 Power Filter 4.1 out of 5 stars (4.1 / 5) See price on Amazon
Fluval U3 Underwater Filter 4 out of 5 stars (4 / 5) See price on Amazon
MarineLand Magnum Internal Canister Filter 4 out of 5 stars (4 / 5) See price on Amazon
Penn Plax Cascade Canister Aquarium Filter 4.1 out of 5 stars (4.1 / 5) See price on Amazon
Aqueon Quietflow Canister Filter 4.5 out of 5 stars (4.5 / 5) See price on Amazon
Polar Aurora Free Media 3-Stage Filter 265GPH 4.2 out of 5 stars (4.2 / 5) See price on Amazon

AquaClear – Fish Tank Filter

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This AquaClear Power Filter comes with almost all features for beginners to fish tanks.

Accordingly, the filters come with the multi-filtration system including mechanical, chemical, and biological filtering stages. Also, the volume is 7x more powerful than comparable filters despite the small size. This filter can pump 100 gallons per hour to ensure the clean Inhabitat all the time for your fish.

Plus, this power HOB filter is easy to install and maintain. You can even custom the filter performance by changing the patented media and filters of AquaClear.


  • Multiple quiet filtration processes
  • 7x boosted performance
  • Easy to install, customize, and maintain


  • Not recommend for sand substrate aquarium
  • Costly replacement for filters

Tetra Whisper Power Filter for Aquariums

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This Tetra Whisper Power Filter is customized to position in-tank. Hence, it is inexpensive and very compact. Interestingly enough, the quality-build and features are still a bang for your buck.

The filter looks a bit plastic-cheap, but it turns out solid and easy to set up. The filtration is good with a smooth flow rate but not excellent. In addition, you might suffer from a buzzing and rattling sound.


  • The cheapest choice on the list
  • Very easy to maintain
  • Built-to-last construction
  • Solid and bare-bone operation


  • So-so filtration media
  • A bit noisy

Fluval C3 Power Filter

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With a capacity to clean over 150 gallons of water per hour, the Fluval C3 Power Filter is right for 20- to 50-gallon fish tanks.

In terms of filtration technology, there are 5 stages available to enhance the three standard filtrations. The first and second stages are to filter mechanical stuff. The next stage deals with chemicals and the last two are biological filtration stages. As a result, the environment in your tank is always clean and healthy.


  • Super effective filtrations
  • Filtration rate that is adjustable
  • Compact and affordable HOB filter


  • Noticeable noise level
  • Not able to handle sand

Fluval U3 Underwater Filter

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For those who might wonder, the underwater filters are so-called the internal filters that we mentioned above. And the Fluval U3 Underwater Filter is particular in this category.

Overall, this gadget is lightweight and pocket-friendly with some surprisingly effective features. Your fish will love it.

In specific, the filtration system can complete three standard filtration requirements using a variable output, two foam pads, and two cartridges. Most interestingly, the unique BioMax in the third stage is currently one of the best biological filtrations. It can maintain oxygen circulation and water flow at the same time.


  • Lightweight and easy to install the filter
  • Quiet operation and filtration
  • Patented BioMax technology
  • 3-year warranty


  • Tight top knob

MarineLand Magnum Internal Canister Filter

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Many of you might be wondering whether this MarineLand Magnum Internal Canister Filter is a 2-in-1 filter for both internal and canister purposes.

Then, we confirm that this is, to tell the truth, a canister filter which is very easy to install thanks to the innovative design.

The filter comes with four filtrations: 3 standard and 1 additional water polishing filtration. This feature helps get rid of even fine debris with the support of a reusable micron cartridge. As a result, the filter can increase the overall efficiency and make the water even cleaner.


  • Highly versatile for various tank sizes
  • Ease of installation and maintenance
  • Super water-filtration efficiency


  • Not very compact for 20-gallon aquariums

Penn Plax Cascade Canister Aquarium Filter

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If you want an advanced canister filter without breaking a bank, Penn Plax Cascade Canister Aquarium Filter is our recommendation.

All in all, this machine is both more affordable and easier to use than many other canister tools.

Specifically, we like the pre-loaded construction, making it fast to set up the filter. On operation, 3 large filter trays are far sufficient to remove all dirt and harmful substances from the water.

Additionally, the flow rate is extremely high – up to 312 gallons per hour. You can even make use of the fast-disconnect tube to control the rate. More surprisingly, all the process is quiet at such a high flow rate.


  • Powerful and cheap canister filter
  • Very quiet and user-friendly
  • High and adjustable water flow rate


  • Small media trays
  • A bit bulky
  • Tricky priming

Aqueon Quietflow Canister Filter

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Aqueon Quietflow Canister Filter is another option when it comes to canister filters for aquariums.

Like the Penn Plax Cascade gadget and other canister filters, this filter is designed with a powerful capacity – up to 400 gallons per hour. Thus, it might be necessarily abundant for 20-gallon tanks. However, you can rest assured that the water is always in the cleanest condition.

What’s more, this filter can work well with both saltwater and freshwater environments.


  • Very versatile for sizes and for both saltwater and freshwater
  • Quite and ultimate powerful at the same time
  • Ease of settings, operation, and maintenance
  • Multiple priming options available


  • A bit abundant capacity
  • Expensive
  • Reports of leaks

Polar Aurora Free Media 3-Stage Filter 265GPH

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Polar Aurora 3-Stage Filter 265GHP is the last but definitely not the least.

As you might already figure out, this canister filter deals with mechanical, chemical, and biological filtrations. Plus, there is an adjustable spray bar to create gentle water current and decrease surface agitation. It helps adjust the output water flow, as well.

The Polar Aurora also comes along with many interesting parts such as a self-priming pump, a 9-watt UV sterilizer, and flexible media trays to add extra efficiency to the filtration process.


  • Surprisingly affordable price
  • Additional accessories included
  • Powerful filtrations


  • A bit bulky and noisy

Last Verdicts

To wrap it up, you should always have a filter in your fish tank. And this best filters 20-gallon aquariums list will help you to make a wise choice.

Of all the choices, we appreciate the Fluval U3 Underwater Filter the most. It is both affordable, compact, easy-to-use, and powerful at the same time.



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