Best 20 Gallon Aquarium Filter Reviews – 5 Top Picks, Guide, FAQs & More

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You’ll agree with us when we say that with so many 20-gallon aquarium filters out there, it can get very confusing to pin down the most suitable one for you. 

We’re here to tell you that it doesn’t have to be confusing. With the proper research and observation, you can find a great filter for your 20-gallon aquarium. 

In today’s post, we’ll discuss the general problems that aquarists run into when buying 20-gallon aquarium filters and delve deep into some of the most popular 20-gallon aquarium filters available. 

Top Pick

This powerful filter works wonderfully and looks great with just about any aquarium. It has a self-priming system that takes the load off of the user.

Runner Up

This product is extremely lightweight and has a very small footprint. It’s great for busy aquarists as it doesn’t require regular maintenance.

Also Great

This filter has a sturdy body that will last you years and comes with a design that doesn’t require priming. The flow rate can be adjusted to your needs.

After testing these filters out for months in different conditions, we can conclusively say that these three are the best ones. 

Now, let’s get into the reviews for the best 20-gallon aquarium filters. 

Best 20 Gallon Aquarium Filter - Top 5 Review

1. Overall Best 20-Gallon Aquarium Filter - Polar Aurora Free Media 3-Stage External Aquarium Filter Review

This product will impress you immediately just by how well-built it is. The body is made from high-quality material that just exudes durability when you touch it. It’s not prone to cracking or damage of any kind and you can rest assured it will last you a very long time. 

It operates very quietly and this quietness remains consistent throughout a long period of time, unlike most filters that claim to be quiet. We’ve been testing this filter for several months and it has shown no signs of becoming loud during operation.

Features of Polar Aurora Free Media 3-Stage External Aquarium Filter – Best 20 Gallon Aquarium filter

  1. Dimensions: 10 inches by 10 inches by 16 inches
  2. Maximum flow rate: 265 gallons per hour 
  3. Adjustable flow rate control
  4. Self-priming pump
  5. Adjustable spray bar
  • Attractive appearance
  • Operates silently
  • Requires little maintenance
  • Easy to assemble
  • Highly sturdy
  • Lightweight for its size
  • Quite large in size compared to most of its competitors

If you’re looking for a reliable and powerful filter that’s easy to use then this is the product for you. It’s quiet and incredibly long-lasting.

2. Best Easy-Maintenance 20-Gallon Aquarium Filter - Marina Power Filter Review

The Marina Power filter really is one of those products that a lot of its competitors use as a benchmark to measure whether their product is up to par or not. It’s a product that shines in pretty much every aspect and has little to no flaws. 

The motor allows it to be incredibly effective and filter water at a very rapid rate. Since the motor is completely submerged underwater, the sound is dampened and the filter works extremely quietly overall. 

It also has a very small footprint inside the tank so your fish will have ample space to swim around if you decide to install this filter onto your 20-gallon aquarium.

Features of Marina Power Filter

  1. Dimensions: 3.8 inches by 11.5 inches by 6.4 inches
  2. Weight: 1.88 pounds
  3. Adjustable flow rate
  4. Comes with 4 filter cartridges
  5. Maximum flow rate: 92 gallons per hour
  • Lightweight for its size
  • Easy to mount
  • Doesn’t take up too much space
  • Highly durable
  • Easy to maintain
  • Its replacement cartridges are quite pricey

If you don’t want to spend too much time maintaining and cleaning your aquarium filter then this is the product you’re looking for. You don’t even need to prime it after cleaning.

3. Best 20-Gallon Aquarium Filter with Quiet Operation - Tetra Whisper IQ Power Filter Review

As is the case with most aquarists taking care of smaller sized aquariums, aquarists with a 20-gallon aquarium are extremely concerned about the noise that their filter will produce. In an environment as small as 20 gallons, a loud filter can be extremely detrimental to the health and well-being of fish. That’s why Tetra decided to construct a filter that provides high-powered filtration while being silent at the same time. 

The filter is remarkably quiet and its performance is also nothing to laugh at. It was able to make the cloudy water inside our 20-gallon aquarium absolutely clear within a few hours of us plugging it in.

Features of Tetra Whisper IQ Power Filter

  1. Dimensions: 6.9 inches by 6 inches by 7.8 inches
  2. Weight: 2 pounds
  3. Motor makes a sound of no more than 40 decibels
  4. Does not require priming
  5. Adjustable flow rate
  • Easy to assemble
  • Extremely silent
  • Lightweight
  • Compact
  • Budget-friendly
  • Some reviews say that the motor burns out after a few months

If you’re worried about loud noise emanating from your filter then this product is ideal for you. It has excellent build quality and is very easy to handle.

4. Best External 20-Gallon Aquarium Filter - Fluval 106 External Filter Review

Fluval has been the brand to beat for quite a while now and products like the Fluval 106 external filter show why. This filter is an external filter so it won’t take up any space inside your tank. It’s very small in size so you can easily hide underneath your aquarium table stand or any other place around your aquarium.  

The in-take strainer is a great feature since it catches a lot of debris before it even reaches the inside of the aquarium filter. This means that the periods between cleanings get extended by a lot. 

Features of Fluval 106 External Filter

  1. Dimensions: 2 inches by 2.8 inches by 7.5 inches
  2. Weight: 5.86 pounds
  3. Clog-proof intake strainer
  4. Aqua-stop valve
  5. Suitable for both saltwater and freshwater aquariums
  • Highly effective
  • Extremely quiet
  • Does not require a lot of maintenance
  • Quite small in size
  • Does not take up any space inside the tank
  • Quite heavy compared to its competitors 
  • Does not perform chemical filtration

If you don’t want to have a filter that crowds up the inside of your 20-gallon aquarium then this product is ideal for you. It’s placed on the outside of the aquarium and even on the outside, it doesn’t take up too much space due to its small size.

5. Best Affordable 20-Gallon Aquarium Filter - Penn Plax Cascade Hang-on Aquarium Filter Review

This product may be cheaply priced but there’s nothing cheap about it when it comes to its build quality and performance. The body is durable and sleekly built to easily blend into all kinds of aquarium environments and its performance is just as impressive as any other product on this list. 

The spray bar it comes with makes it extremely easy to control the direction of the flow of water coming out from the filter and it also ensures that water is being effectively circulated to every corner of your 20-gallon aquarium.

Features of Penn Plax Cascade Hang-on Aquarium Filter

  1. Dimensions: 6.5 inches by 6 inches by 5 inches
  2. Weight: 1.75 pounds
  3. Maximum flow rate: 100 gallons per hour
  4. Adjustable flow rate knob
  5. Suitable for both fresh and marine aquariums
  • Inexpensive
  • Quiet
  • Easy to clean and maintain
  • Quite compact
  • Lightweight
  • Some reviewers say that the self-primer has some working issues 
  • Tubes are a little inflexible and difficult to handle

If you’re looking to save some money but still want a reliable and effective filter for your 20-gallon aquarium then this product was made for you. It’s suitable for all types of aquariums and it’s light on the pocket.

best 20 gallon aquarium filter

Buyers’ Guide

What are some things to look for in a 20-gallon aquarium filter?

20-gallon aquariums are by some of the most versatile types of fish tanks and they are popular among both beginner as well as veteran fishkeepers. This is why there are a lot of different types, shapes and sizes of 20-gallon aquarium filters available out there which focus on different aspects of a 20-gallon aquarium. Some things to look for in a 20-gallon aquarium filter that can help you narrow down your search are: 

  • Priming Mechanism 

Priming refers to getting the filter ready for operation before you can start it. Priming is necessary because if you don’t do it, you run the risk of burning out your filter’s motor and permanently damaging it, sometimes beyond repair. Priming needs to be done every time your filter is disconnected from its position on the aquarium. So, you have to prime a filter every time you do maintenance and cleaning of it as well as if you disconnect it entirely from your aquarium for whatever reason. 

If you don’t want the hassle of having to prime your 20-gallon aquarium filter every time you clean it then you might want to invest in a filter that has a self-priming system.

  • Ease of Maintenance 

Of course, maintenance is a crucial part of all aquarium equipment and with filters, it’s especially important because if a filter isn’t maintained properly, the rest of the maintenance on your aquarium won’t really be that effective either.

Keeping this in mind, you should look at what filter you’re getting and opt for one that is relatively easy to maintain and clean. These days, filters come with streamlined designs that are easy to disassemble and clean. 

If you don’t get a lot of time to perform maintenance on your aquarium filter then opt for one that doesn’t require a lot of regular maintenance.  

How do I securely install my 20-gallon aquarium filter? 

This can vary significantly depending on what type of filter you have but we’re going to be talking about in-tank filters in this answer due to the fact that most 20-gallon aquarium filters are in-tank filters. 

In-tank filters are relatively easy to install onto an aquarium. All you have to do is decide on the location, position your filter securely and secure it onto your aquarium using the suction cups or whatever other mechanism that the manufacturer has provided. Once the filter is secured, fill it up with aquarium water using a cup; this is known as priming. If you have a filter that doesn’t require priming, you can skip this step. Next, check to see that all the tubes and wires are securely connected and then turn your filter on. 

What types of filters are most appropriate for 20-gallon aquariums?

As we’ve mentioned briefly above, in-tank filters are the most common types of filters usually found in 20-gallon aquariums. These include both HOB filters that hang on to aquarium walls or fully submersible filters that are found within the aquarium water. 

How can I keep my 20-gallon aquarium filter clean? 

The main culprit when it comes to filters becoming dirty too easily is excess food lying around inside your aquarium. This uneaten food gets swept up by your filter and as a result, your filter gets clogged. We highly recommend that you be wary of how much food you’re giving to your fish. Give them only as much as they need and try to ensure there is no food leftover inside the tank and if there is, make sure to scoop it out using a fish net or a gravel cleaner. 

Another great way to keep your 20-gallon aquarium filter clean is to baffle the opening with a sponge or something similar. This sponge will help catch any large waste or debris before the water even reaches your filtration media inside. If you decide to do this, you have to ensure that the flow rate of your filter is not affected too much. 

Is it possible to over-filter an aquarium?

There’s no such thing as over-filtering an aquarium but too powerful of a filter can create a flow inside an aquarium that is too stressful for your fish. 

Frequently Asked Questions

What can I do about a noisy 20-gallon aquarium filter? 

The first thing you should do is definitely a thorough cleaning of your 20-gallon aquarium filter. This might help fix the noise problems you’ve been having with it and even if it doesn’t, you’ll still be able to identify much easily what the source of the noise is as a result of the cleaning. 

Another thing you should try is lubing the impeller and motor of the filter so they run smoothly. You can utilize silicon oil for this or even just regular Vaseline. 

What size filter would be most appropriate for a 20-gallon aquarium?

The general rule of thumb when it comes to filters is to have a flow rate that is 4 times that of the size of the aquarium. Flow rate refers to the amount of water that a filter is able to clean within an hour. So, if you have a 20-gallon aquarium, you’re going to need a filter with a flow rate of at least 80 gallons per hour. 

What can I do if my filter is creating currents that are too strong for my fish? 

The first thing to do is to find out whether your filter comes with the option of adjustable flow control or not. If it has adjustable flow control then there’s really no problem at all. All you have to do is lower it until you find the appropriate flow rate that doesn’t disturb your fish. 

If it doesn’t have flow control then you’re going to have to look at some DIY fixes for your 20-gallon aquarium filter. We mentioned above how tying a sponge to your filter’s inlet pipe can help keep it clean, you can do the same with the outlet pipe of the filter in order to control the flow rate. 

Can my 20-gallon aquarium filter help combat algae?

Most standard 20-gallon aquarium filters are not equipped to help combat algae. While it’s true that some filters can sweep up small, free-flowing algae, that does not mean they can help eliminate it completely. If you want a filter that can help eliminate the algae in your 20-gallon aquarium then we suggest getting a filter that also has a UV sterilizer built into it. A UV sterilizer uses UV light to kill bacteria and algae inside your aquarium. 

What should I do in the case of a power outage? 

We highly recommend that you have a secondary filter available that runs on batteries. This filter can help take care of your fish until the power comes back on. 

If you don’t have such a filter available then you can perform regular water changes to keep the tank clean until the power comes back. 

How long can fish survive in a 20-gallon aquarium without a filter?

Most fish are able to survive in a 20-gallon aquarium without a filter for a little more than 24 hours. After that, the ammonia levels rise to a point where your fish will start having trouble breathing. Although many fish can survive for more than 24 hours, we highly recommend that you don’t let your fish go without a filter for more than a few hours because as the oxygen levels start to drop, it can cause a lot of stress to your fish. 

What should I do if something gets stuck in my 20-gallon aquarium filter?

The most immediate and obvious thing to do is turn off your filter. If it’s a fish or any other living being, you don’t want the moving parts inside your 20-gallon aquarium filter to harm them any more than they already have. Next, you should start disassembling your aquarium filter. Note that you should do this inside the aquarium water if you believe that the thing stuck inside it is one of the living inhabitants of your aquarium. Once you’ve disassembled it and identified what was stuck inside it, take it out. If it’s a living being, release it into your aquarium; if it’s not, discard it. 

Can I use a 30-gallon filter on a 20-gallon aquarium? 

Yes. A 30-gallon filter is not that far off and you can definitely get away with the flow rate it offers without disturbing your fish too much. If you do feel that the flow rate is disturbing your fish then you can employ the sponge baffling technique we’ve described in one of our answers above. 

Should I turn my 20-gallon aquarium filter off during water changes? 

Yes. Turning your 20-gallon aquarium filter off during water changes is a good idea as it stops the flow of water circulating inside the aquarium and allows you to scoop out the old aquarium water a lot more effectively. 

Should I turn my 20-gallon aquarium filter off at night?

No. A filter is not the same as an aquarium light. A filter needs to be running constantly in order to be effective. According to a study, the beneficial nitrifying bacteria inside an aquarium start dying just 30 minutes after the filter is turned off. Thus, you should never turn off your 20-gallon aquarium filter if you want your fish to be healthy and happy. 

Final Verdict

20-gallon aquarium filters can in many different varieties so it’s important you do your research properly to find one that’s most well-suited to your needs.

After weeks of arguments and debates, we’ve concluded the Polar Aurora Free Media 3-Stage External Aquarium Filter to be the best of the bunch. It looks beautiful, it’s a filtration beast and it’s not even that expensive. 

And with that, we’re at the end of our post for the best 20-gallon aquarium filters. 

Give us feedback and let us know what filter you’re using in your 20-gallon aquarium.

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