5 Best Filters for 20-Gallon Tanks: Select the Right One for Your Needs (Summer 2022)

Here, you'll find reviews of the top 5 aquarium filters for 20-gallon tanks and a list of features to look out for when purchasing one.
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Last updatedLast updated: July 16, 2022
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The most crucial piece of aquarium equipment is the filter. Not only does it keep the water clean, but it also provides a favorable environment for fish. In this article, we will review five of the best filters for 20-gallon tanks. We will discuss the pros and cons of each filter, and give you some pointers on choosing one.

We took into account the type of filter, its ease of use, flow rate, noise levels, and filtration stages when we chose our top five finalists. So, whether you are looking for a new filter for your existing tank or are in the market for a new 20-gallon aquarium, one of these options is sure to fit your needs.

Top 5 Filters for 20-Gallon Tanks Review 2022

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Editor’s Choice

AquaClear Fish Tank Filter

Features
  • Type: HOB power filter
  • For Tanks: 10-30 gallons
  • Flow Rate: 150 GPH
  • Filtration: 3-stage
  • Dimensions: 4.5 x 8.2 x 6.7 in.

More features: lifetime warranty; easy installation; comes with AquaClear foam, activated carbon filter and BioMax ceramic rings

The AquaClear 30 Fish Tank Filter tops our list of the best filter for a 20-gallon tank. This is a hang-on-back power filter that features a nice flow rate of 150 GPH. Its foam inserts and activated carbon filter inserts help remove toxins and odors from the water. The BioMax ceramic rings provide biological filtration, and the filter has a patented re-filtration system that makes sure the water in your aquarium is clean and clear. Plus, it comes with a lifetime warranty.

The AquaClear 30 Fish tank filter is almost identical with its equally famous brother, the AquaClear 20. They are both power filters with a 3-stage filtration system but the AquaClear 30 has a higher filtration volume. You can use in tanks that hold up to 30 gallons of water whereas for the AquaClear 20 can only work in 20-gallon tanks.

Why are we impressed?

  • Works great for both freshwater and saltwater aquariums
  • Lifetime warranty
  • Compact
  • Easy to use and install
  • Affordable price
  • Energy-efficient
  • Nice filtration volume

What negatives must you be aware of?

  • Creates vibrational sound from time to time
  • There might be occasional flow problems
RELATED: 5 Best Filters for Axolotl That Are Safe, Reliable, and Effective in Keeping Water Clean (Summer 2022)
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Features
  • Type: canister
  • For Tanks: up to 30 gal.
  • Flow Rate: 115 GPH
  • Filtration: 4-stage
  • Dimensions: 11.5 x 9 x 13.5 in.

More features:  large capacity media baskets; easy push button primer; comes with 2 poly fiber floss pads, 1 coarse bio-sponge, and 1 bag of activated carbon.

If you’re looking for an aquarium canister filter that is perfect for tanks up to 30 gallons, the Penn-Plax Cascade 500 canister filter is a great option to consider. This filter comes with four stage filtration and can handle both freshwater and saltwater aquariums. Plus, it has two independent valve taps that rotate 360°, making it easy to adjust the water flow. And, with its large capacity media baskets, you can easily customize your filter media setup. The Cascade 500 also has a spout that you can use to direct the water flow where you want it. This is really helpful if you have a specific area of your tank that you want to target with the filtration. For example, if you have a lot of algae on one side of your tank, you can use the directional spout to send more water flow in that direction and help to clear it up. Additionally, the spray bar can help to create more water agitation and oxygenation in your tank, which is beneficial for both your fish and your plants.

The Penn-Plax Cascade 500 Aquarium Canister Filter is our upgrade pick because it is a more powerful filter than the AquaClear 30 with a 4-stage filtration system. Also, it has a better user-friendly design with a push-button self-primer that makes it simple to get the filter up and running. However, it has a lower flow rate than the AquaClear 30 Fish tank filter.

What makes it stand out?

  • Works quetly
  • Large media trays
  • Easy-to-use and install
  • Compatible with freshwater and saltwater aquariums
  • 3-stage filtration
  • Attractive design
  • Adjustable flow rate

Which disadvantages must you keep in mind?

  • Filter media can be expensive
  • It might be difficult to make the primer smooth again after replacing the filter
  • The power consumption is a bit high
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Features
  • Type: HOB power filter
  • For Tanks: 20 – 50 gal.
  • Flow Rate: 153 / 137 GPH
  • Filtration: 5-stage
  • Dimensions: 7 x 5 x 7 in.

More features: designed for freshwater and saltwater aquariums; patented refiltration system; adjustable flow, telescopic intake tube

The Fluval C3 HOB filter is designed for both freshwater and saltwater fish tanks, and features 5-stage filtration. With two mechanical filtration stages, a chemical filtration stage with activated carbon, and a biological filtration stage, this filter can handle all of your needs. The patented refiltration system ensures that your water is always clean and healthy, while the adjustable flow allows you to customize the flow rate to meet your needs. The telescopic intake tube helps to reach deep in your tank, and the Bio Screen pad helps to keep the tank healthy and bacteria-free.

The Fluval C3 has a lot in common with its predecessor Fluval C2. It is a worthy upgrade as it can work in bigger tanks of up to 50 gallons thanks to its higher filter circulation rate. Although it is recommended for 20 to 50 gallon tanks, you may want to consider the Fluval C2 if you have a 30 gallon or smaller fish tank for gentler water flow.

What do we love it for?

  • Nice flow rate
  • Excellent five-stage filtration
  • Easy to clean
  • Easy-to-access media compartment

What were we disappointed with?

  • Foam pad need to be replaced every few months
  • The impeller is a bit hard to clean
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Features
  • Type: internal canister filter
  • For Tanks: up to 90 gal.
  • Flow Rate: 290 GPH
  • Filtration: 3-stage
  • Dimensions: 8.5 x 5.81 x 11 in.

More features: submerged motor; versatile filtration; high-efficiency polishing with the micron cartridge

The MarineLand Magnum Polishing ML90770-00 Filter converts to water polishing, making it a versatile option for aquarium filtration. It can pump 290 gallons of water every hour and works well for tanks up to 90 gallons in size. This filter is suitable for freshwater or saltwater tanks, and it features a 3-stage filtration system with a submerged motor. The Rite-Size floss sleeve makes sure your tank is clean and free of debris, while the Black Diamond Premium Activated Carbon provides 153 square inches for the growth of Bio Spira. This filter is also reusable, so you can keep your tank looking great for years to come.

The only fish tank filter that comes close to the MarineLand Magnum Polishing ML90770-00 Filter is the popular MarineLand Magniflow c360. Although the latter is an external canister filter with a higher filter capacity, the ML90770-00 is a better space saving option. Plus, there isn’t much difference between the 2 models’ filtration capacity as the c360 filters up to 100-gallon tanks.

What are its best features?

  • Nice flow rate
  • Three-stage filtration
  • Customizable media capacity
  • Water polishing option
  • Easy to maintain
  • Self-priming
  • Durable construction
  • Quiet operation

What could be improved?

  • A bit bulky for small aquariums
  • Included media is not good enough
  • May spoil the view as it is placed inside the aquarium
RELATED: 5 Best Canister Filters for 55-Gallon Tanks – Versatile and Effective (Summer 2022)
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5
Best Flow Control

Fluval U3 Underwater Filter

Features
  • Type: underwater
  • For Tanks: up to 40 gal.
  • Flow Rate: 290 GPH
  • Filtration: 3-stage
  • Dimensions: 12 x 6 x 5 in.

More features: designed for freshwater, saltwater and reptile environments up to 40 gallons; horizontal or vertical mounting; flip-top lid; quiet operation

If you’re looking for an underwater filter for a 20-gallon tank, the Fluval U3 is a great option. The Fluval U3 Underwater Filter works great for freshwater, saltwater and reptile environments up to 40 gallons. It features 3-stage filtration with a 290 GPH flow rate. With the flip-top lid it is really easy to access the filter media, and the Adjustable 3-Way Flow Control lets you customize the water flow. The Integrated Spray Bar creates a natural waterfall effect, and the sleek design adds style to your aquarium.

The Fluval U3 is an upgrade of the Fluval U2 and the 3rd model in the Fluval U series of aquarium filters. The two models are completely different making the U3 a worthy upgrade. The U3 has a higher wattage, filtering capacity and pump output.  It is also a better performer when compared to other 3-stage filters on this list like the AquaClear 30 but you would have to dig a little deeper into your pockets for it.

What makes it stand out?

  • Silent operation
  • Easy to assemble and install
  • Easy to remove filter media
  • Three output modes
  • Lightweight
  • 3-stage filtration
  • Great warranty
  • Budget-friendly

Which disadvantages must you keep in mind?

  • Rather small media space
  • A bit bulky for a small tank
  • The top knob for flow changing feature is a bit too tight to turn
  • Occasional drop in flow

Things to Consider

Choosing the right filter for your 20-gallon aquarium is not an easy task. There are many factors to consider, such as the type of fish you intend to keep, and the amount of maintenance you are willing to do among other features. Here, we’ve provided a buyer’s guide to help you choose the best filter for your needs.

Why Buy a Filter for a 20-Gallon Aquarium?

A filter is a key piece of equipment for any aquarium. It not only cleans the water, but also helps to regulate the temperature and oxygen levels. In a small tank like a 20-gallon, it’s especially important to have a good filter, because without one the water can become dirty and polluted very quickly.

What Type of Filter to Choose for a 20-Gallon Aquarium

5 Best Filters for 20-Gallon Tanks: Select the Right One for Your Needs (Summer 2022)

Power (HOB) filters and canister filters are the most popular types of filters in the market today

There are a few different types of filters that are best for 20-gallon tanks. The main types are:

Undergravel Filters

Undergravel filters are among the most popular types of filters for small tanks. They operate by pumping water up through a tube and then releasing it over the gravel at the bottom of the tank. This causes the gravel to filter the water, which removes dirt and debris. Undergravel filters are easy to install and relatively inexpensive. However, they can be difficult to clean and may not be suitable for larger tanks. If you’d like to know more about this type of filter, read our article on how an undergravel filter works.

Canister Filters

Canister filters are another popular type of filter for small tanks. They work by pumping water up through a tube and into a canister that contains the filter media. This media can be anything from activated carbon to gravel or foam. The best canister filters are easy to set up and relatively inexpensive. However, they can be difficult to clean and may not be suitable for larger tanks.

HOB Filters

HOB stands for “hang on back” and refers to the type of filter that hangs on the back of the tank. HOB filters are one of the most popular types of filters because they are easy to use and come in a variety of sizes. They work by pumping water up through a tube and into a filter media. This media can be anything from activated carbon to gravel or foam. HOB filters are easy to set up and relatively inexpensive. However, they can be difficult to clean and may not be suitable for larger tanks. If this is the type of filter you are most interested in, check out our reviews of the best Hang-On-Back filters for different size aquariums.

UV Sterilizers

UV sterilizers are a type of filter that uses ultraviolet light to kill bacteria and algae in the water. They are a popular choice for tanks with salt water fish or coral because they help to keep the tank healthy. UV sterilizers are relatively expensive but can be worth the investment if you have a tank with sensitive fish or coral.

Factors to Consider When Buying a Filter For a 20-Gallon Tank

When it comes to purchasing a filter for your 20-gallon fish tank, there are a few factors you need to consider. They are:

Number and Type of Fish

5 Best Filters for 20-Gallon Tanks: Select the Right One for Your Needs (Summer 2022)

Take into account what kind of fish you are going to keep in your aquarium before purchasing the filter

The type of fish you have in your tank is another factor to consider. Some fish require a more powerful filter than others. If you have a lot of fish or if you have fish that produce a lot of waste, you will need a more powerful filter.

Filter Capacity

The first thing to consider is the size of the filter. You want to make sure that the filter can handle the size of your tank. Most filters are rated by their gallon capacity, so be sure to choose a filter that is large enough for your tank.

Filtration Stages

Some filters have multiple filtration stages. This means that the water goes through a series of different filters before it is released back into the tank.

Most filters have a mechanical stage, which removes debris from the water, and a biological stage, which helps to break down waste products. Some filters also have a chemical stage, which uses chemicals to remove pollutants from the water.
If you are looking for a more thorough cleaning, you may want to choose a filter with multiple filtration stages.

Type of Media

The type of media that the filter uses is also important to consider. Different filters use different types of media. Some filters use activated carbon while others use foam or gravel. You may want to choose a filter that uses the type of media that you prefer. In case you are unsure what media to use, we have compiled the list of the best aquarium filter media you might want to check out.

Flow Rate

5 Best Filters for 20-Gallon Tanks: Select the Right One for Your Needs (Summer 2022)

Make sure the flow rate is high enough so your fish gets the amount of oxygen it needs

The flow rate is the amount of water that the filter can pump per minute. The higher the flow rate, the more water the filter can clean in a shorter amount of time. You want to make sure that the flow rate is high enough to keep your fish healthy. If the flow rate is too low, your fish may not get enough oxygen and could become sick.

Maintenance

How much maintenance you are willing to do is also important to consider. Some filters require more maintenance than others. If you are not willing to do a lot of maintenance, you may want to choose a filter that is less demanding.

Priming

Some filters require priming before they can be used. This means that you have to pump water into the filter before it will start working. If you are not willing to do this, you may want to choose a filter that does not require priming.

Size and Weight

When choosing a filter, you also need to consider the size and weight of the filter. Some filters are large and heavy and may be difficult to move around. Others are small and lightweight and easy to transport.

Price

The price of a filter can vary depending on the size, brand and type of filter. You can expect to pay anywhere from $20 to $200 for a quality fish tank filter.

Other Features

Some filters come with additional features such as a built-in heater or a UV sterilizer. If you are looking for a filter with these features, you will likely pay more money.

How to Maintain Your Aquarium Filter

5 Best Filters for 20-Gallon Tanks: Select the Right One for Your Needs (Summer 2022)

Remember that your filter needs regular cleaning and maintenance

Once you have chosen a filter for your aquarium, you need to make sure that you maintain it properly. This involves doing regular cleaning and replacement of the media. Here are some tips on how to maintain your aquarium filter:

Cleaning

You should clean your filter at least once a month. This involves removing the media from the filter and rinsing it in water. You should also clean the housing of the filter with water.

Replacing Media

The media in your filter will eventually wear out and need to be replaced. You should replace the media every 3 to 6 months, depending on how often you clean your filter.

Heating Element

If your filter has a heating element, you will need to check it regularly to make sure that it is working properly. The heating element should be kept clean and free of debris.

UV Sterilizer

If your filter has a UV sterilizer, you will need to replace the light bulb every 6 to 12 months.

FAQ

There is no one-size-fits-all answer to this question. You need to consider the size and type of fish you have in your tank, as well as the other factors listed above.

This will vary depending on the type of filter you are using and how often it is used. Generally, you should change the filter every 6 to 12 months.

The best way to tell if your filter is working properly is to check the water clarity. If the water is clear, your filter is working correctly. If the water is cloudy, you may need to replace the filter. You should also check the heater to make sure it is working properly.

If your filter stops working, you will need to replace it immediately. Do not try to fix it yourself – this could damage the filter and could be dangerous for your fish.

No, a filter can’t be too big for a tank. However, you need to make sure that the flow rate is high enough to keep your fish healthy. If the flow rate is too low, your fish may not get enough oxygen and could become sick.

Our Verdict

When choosing a filter for a 20-gallon tank, you need to consider all the factors listed above. Our top three picks include the AquaClear 30 filter, the Penn-Plax Cascade 500 canister filter, and the Fluval C3 power filter.

The AquaClear 30 Fish Tank Filter is compact, easy to use and install, and has a nice filtration volume. It is also energy-efficient and affordable, and comes with a lifetime warranty.

The Penn-Plax Cascade 500 Aquarium Canister Filter comes with four stage filtration and can handle both fresh and salt water. Plus, it features an adjustable water flow, and an easy push button primer.

The Fluval C3 Power Filter offers excellent five-stage filtration. This filter also has a nice flow rate, and features an easy-to-access media compartment, making it a breeze to keep your tank clean and healthy.

Thank you for choosing our article on the best filters for 20-gallon tanks. If you have any questions or comments, please let us know. We would love to hear from you! ​​​​​​​​​​

References

1.
Aquarium Filtration: The total picture | Tetra
One of the most important parts of fishkeeping is also one of the easiest. Just like an air filter cleans the air we breathe, an aquarium filter cleans the water your fish breathe.
2.
15 Common Fish Tank Problems and How to Avoid Them
Aquarium keeping is a fun and rewarding activity that can provide years of enjoyment, education and even stress relief. When you’re new at it, however, it’s easy to do things that might not be good for your fish or your stress level.
3.
BIOLOGICAL FILTRATION IN AQUARIUMS - Fluval USA
While there are 3 key forms of aquarium filtration (mechanical, chemical, and biological), the latter ranks as the most important in aquatics.
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