10 Best Filter For 20 Gallon Aquarium in 2021 | Reviews & Guide

There is nothing in this world compared to the beauty of ocean life, and I know anyone who is a fish lover will agree with me. Now imagine bringing all that beauty to your home. That’s right; I am talking about an aquarium.

Aquariums need to be clean and free from germs for the safe lives of your lovely fish. To ensure the cleanliness, you will need a filter. I am here to show you the best filters for a 20-gallon aquarium available to you that will make your aquarium cleaner and safer for you and your fish.

Best Filter for 20 Gallon Aquarium Comparison Chart

Product NameBrandSizeWeightPrice
Aqua Clear - Fish Tank FilterAqua Clear20 gallons1.69 pounds
Whisper IQ Power Filter for Aquariums, With Quiet TechnologyTetra ®20 gallons2 pounds
Whisper In-Tank Filter with BioScrubber for aquariumsTetra ®Up to 20 gallon1.32 pounds
Tetra Whisper EX Silent Multi-Stage Power Filter for AquariumsTetra ®30-45 gallons1 pound
MarineLand PenguinMarineLand20-30 gallons1.86 pounds
Marina Power FilterMarinaUp to 20 gallons1.88 pounds
Fluval C Power FilterFluval20-50 gallons1.92 pounds
Aqueon Quietflow E Internal Power FilterAqueon20 gallons7.2 ounces
Penn Plax Aquarium Cascade Canister FilterPenn Plax20 gallons10.1 ounces
Tetra Whisper Power Filter for Aquariums, 3 Filters in 1Tetra ®Up to 20 gallons1.56 pounds


Best Filter for 20 Gallon Aquarium Reviews

After extensive research, we have found some of the best aquarium filters available for you. Now, these aren’t all of them, but they are those that top the charts. This review will help you find a filter that is the best for your aquarium. Without further ado, let’s get into it.

You can’t talk about aquarium filters and not mention the Aqua Clear filter. There are up to five models of the Aqua Clear filters. One thing they all have in common is that they have cover more media volume, up to 6 times more than any other. It also has a re-filtration system that gives you control over the flow rate without interfering with the filtration efficiency.

What I like

The filter has a multi-stage filtration system that not only cleans the aquarium, but it also ensures you retain the necessary bacteria that is required to remove toxic ammonia and nitrite. Another thing that sticks out about this filter is that this hang-on filter is easy to clean with clear instructions on how to clean the top, middle, and bottom parts of the filter.

What I don’t like

The filter produces a loud vibration that can be annoying and unsettling for the fish or other pets. Something else that turned me off about this filter is that the later models don’t last for a long time and requires you to replace it more often than I would like, making it too costly.

You should make sure to clean the aquarium every two weeks. Doing this will ensure you get maximum operation and efficiency from the filter. It is also necessary to unplug the filter before cleaning. Also, replace the Foam Filter Insert after every two months.

  • Easy to assemble and install the parts
  • Only needs minimal space for installation
  • Different sizes for different tank sizes
  • Has a coarse sponge for cleaning impurities
  • Has long water to filter to media contact
  • Irritating loud sound when operating
  • Costly, as you will need to replace parts often

The Whisper IQ power filter is what you should turn to if you want an efficient and quiet filter. It uses SoundShield technology to block noise between the motor and the filter. It also has vibration dampening technology. Combine these two, and you get a tranquil and long-lasting machine.

What I like

First off, it would have to be the sound canceling and vibration dampening technology that allows you to have a quiet operation. The filter also uses StayClean technology that makes maintenance easier and healthier fish. One other thing worth mentioning is that the motor starts up immediately without any need for priming.

What I don’t like

Although the system will work fine eventually, it takes a village to get it started. You might need to clean the filters for it to work correctly frequently. You may also need to change the cartridges every few days; otherwise, you will have an ugly fish tank with brown water.

You can reduce the flow to as low as 10 GPH for plants, feeding, or other needs that require a low flow. You can also adjust the intake to fit your aquarium and use the smart path spillway to oxygenate the water.

  • The quietest aquarium filter in the market
  • The motor is self-priming
  • Has StayClean technology that ensures cleanliness at all times
  • It has a bio scrubber that encourages healthy bacteria to remove toxic nitrites and ammonia.
  • Reduces buildup on the glass
  • The filter is color-coded, making it easy to place the cartridge correctly.
  • Might need frequent cleaning during the first weeks
  • Can burn your heater when the water level is too low
  • It is not as quiet as advertised.

Tetra is back with yet another filter. This one is installed on the inside of the aquarium, which makes placement easy. Since it is an in-tank filter, it is quieter than most and can function in water that is as little as 2 inches high.

What I like

This model has two filters in one, which I must say is a sweet deal. It uses tiny filter cartridges that can be easily adjusted depending on the water level. I was also impressed by the use of bio-bag filters. These filters prevent discoloration of the aquarium water due to fish food. The filters also do a great job of absorbing dirt, grime, and other particles through the use of activated carbon.

What I don’t like

I have praised this filter, and this is because of the spectacular work it does, but it is not without its downsides. The filter has a strong suction power. While this might not sound like a bad thing, it might be hazardous to little fish. They can get sucked in and harmed.

Since this is an in-tank filter, you need to be careful with the measurements. You want to make sure that it fits into your tank; otherwise, it will be submerged and will not be able to clean. Know your aquarium’s measurements and get the correct filter size.

  • Easy to clean
  • Super quiet
  • Durable
  • It uses bio-bag filters
  • It can be used in both terrariums and aquariums
  • Has two filters in one
  • Has a space-saving design making it ideal for small tanks
  • Requires frequent cleaning
  • Little fish might get sucked in due to strong suction power

Whenever you need aquarium filters, you don’t need to look any further than the Tetra brand. It brings to you yet another filter in the form of the Tetra Whisper Multi-Stage power filter. And the best news of all, the filter doesn’t need any priming so that you can use it straight from the box.

What I like

This filter has a bunch of features that I like. One of them is the filter cartridge carrier. Forget getting your hands dirty and unnecessary dripping; you now have something that takes care of all that. One other feature is the Timestrip technology. This new design tells you when it is time to change your carbon filter, which happens when the time strip changes from white to red.

What I don’t like

And now for the negatives. One thing that put me off of this filter is that its sand and grit can get sucked into the filter, causing malfunctions and a noisy sound. To combat this, you would have to clean the filter regularly.

  • Small and compact design
  • Time strips that alert you when it’s time to change the filter
  • Has two bacteria growth plates that check the aquarium’s cleanliness
  • Two carbon filters that keep the water clean
  • Quiet operation
  • Can suck in dirt and grime

Anyone who claims to love their fish has to check out the Marineland bio-wheel penguin filter, post haste. This is one powerful but quiet machine that you have to have. It provides you with a natural three-stage filtration; mechanical, biological, and chemical filtration. What more could your fish ask for?

What I like

Now to my favorite parts of the filter. I have to mention how excellent its cleaning powers are, and this is due to the 3-stage filtration discussed above. The mechanical filtration gets rid of small particles, the biological helps avoid water discoloration and odor due to buildup of bacteria and algae, and the chemical filtration removes toxic ammonia and nitrites. The filter is also effortless to set up and operates very quietly.

What I don’t like

One of the problems that I had with this filter is that it has no flow rate adjuster. This means you can’t adjust the water flow rate, and you might, therefore, have to deal with a waterfall-like sound.

  • Three-stage filtration for clean, clear water
  • Quiet operation
  • Easy to set up
  • Adjustable strainer
  • Efficient cleaning
  • Doesn’t have a flow rate adjuster

If you are looking for a filter that combines practical and aesthetic benefits, this is the one for you. Not only does it have an elegant design, but it also takes up less space than any other filter. It has an adjustable flow control that gives you power over the water flow level in your aquarium.

What I like

I like the self-priming feature of the filter. It allows you to go about your work without having to check on it from time to time. You won’t find any dirt or grime clogging it up. Another attractive feature is the adjustable flow control and the small space that the filter takes thanks to its small size. It even gives the fish more space to swim in.

What I don’t like

The big downer with this filter is the filtration capacity. It has such a small filtration capacity that it takes a long time to clean up waste from two or three small fish.

  • Super quiet operation
  • Self-priming feature
  • Takes a little space in the aquarium
  • Has an adjustable flow control
  • Easy maintenance
  • It has a small filtration capacity

Here is one unique filter. We have been talking endlessly about filters with three filtration stages. Now the Fluval C power comes with FIVE filtration stages. This filter also has a powerful motor that makes it easy for it to clean both large and small aquariums.

What I like

Did I already mention the five-stage filtration? This is the one thing that I cannot get over. You cannot get clearer, cleaner water with any other filter. Something else that I liked it has a filter with a clogging indicator. This will alert you when there is buildup of waste even though you may not have noticed it from the outside.

What I don’t like

One thing that I disliked is the noise level. It is not very loud, but the noise increases when you slow the filtration flow. This means you won’t be able to keep it in your bedroom or office because of the sound.

Something else that irked me was that the filter could not handle sand. It is not suitable for you if you have a sand substrate. You might damage the filter and make it have a loud and scratchy sound.

  • Five filtration stages
  • Clogging indicator
  • It has an adjustable filtration rate
  • Small and compact size that doesn’t take up space
  • Suitable for both big and small aquariums
  • The noise level is a bit high
  • The filter cannot be used with fine sand substrates

What is it that is said about internal power filters? That’s right that they have a quiet operation. The smooth operation is even included in the name of the filter itself. Well, what more are you looking for in filters, especially when it comes to the super quiet ones?

What I like

Now to the fun part, the likable features. One of them is the fact that you can position this filter; however you like, whether vertically or horizontally, creating more swim space for your fish. We have already touched on the super quiet operation of this filter, but it doesn’t hurt mentioning it one more time. One other thing I like is the adjustable water return. This feature makes it easy to have clean water at all times without cleaning.

What I don’t like

What is disappointing about this filter is the time it takes to restart after replacing the water. The restart time is longer than I like.

  • Completely submersible
  • Super quiet operation
  • Can be placed either horizontally or vertically
  • Adjustable water return
  • Three-stage filtration system
  • Takes a long time to restart after replacing water

Don’t get discouraged by the fact that it at the bottom two spots; this doesn’t make it any less effective. It’s only just you can’t well place all of them at the same spot. This filter can rotate 360 degrees that make it easy to maneuver in the tightest of aquariums, ensuring a clean aquarium no matter the size.

What I like

One of the things that stuck out immediately to me was that it had a powerful motor. It can provide up to 115 GPH, powerful for aquariums up to 30 gallons. It also has flow valves that make a full revolution for complete cleaning even in small aquariums. It also has a push-button primer that only requires a few pushes to clean prime the filter. One other thing is the use of different media like the floss pad and the coarse sponge for a clean filter.

What I don’t like

The filter has a lot of bypasses because the trays don’t fit correctly. Some gaps make the water overflow. And this might only have happened to me, but the noise level was a bit too high for my liking.

  • Three-level filtration that keeps the water clear
  • Has two large media baskets that can be customized according to your needs
  • Has an easily accessible and easy to push the primer button
  • Airtight seal for proper flow rate
  • Fully rotating flow valves that clean even the smallest of aquariums
  • A lot of bypasses
  • Might be too noisy for your liking

We come to the end of our product reviews, and we have to end with a favorite, a Tetra filter. It has a quiet 3-stage filtration system for a clean and thriving aquarium. The filters eliminate toxic nitrites and ammonia, leaving you with a super clean aquarium. It also includes the Whisper cartridges that, as you can guess from the name, are very quiet.

What I like

The first likable feature about this filter is the Whisper cartridges that allow for quiet and efficient operation. You also get a flow control feature that lets you reduce the flow for better feeding and extended cartridge life.

What I don’t like

For me, the filter did not have such a long life. The motor died after a few months of use. The motor started stalling after just a few weeks, and it finally stopped altogether. Thanks to the excellent customer service, however, I got it replaced.

  • Quiet and efficient operation
  • Flow control feature
  • Three-stage filtration system
  • Uses bio-bag filter cartridges that remove odor and discoloration
  • Long-term use due to lack of moving parts
  • Might be hard to set the propeller in place so can be noisy

Buying Guide

Now that we have looked at the individual product reviews let us move on to what you should look for when buying an aquarium filter. These are things that will help guide you through purchasing the filter that will best suit your aquarium.


One of the most critical factors you should always look for no matter what you’re buying is the brand. You want to buy your filter from a trusted brand. This ensures you get the best quality product available. Make sure you always look for a popular, trusted brand, and they will never disappoint.

Filtration processes

Since you are buying a filter for filtration, you have to look at the various filtration processes that it uses. There are different stages of filtration, and depending on the type of filter, it can have one or all of them. These processes include mechanical, chemical, and biological filtration. The mechanical filtration keeps waste particles away from the water; the biological filtration removes harmful bacteria and fungi while the chemical filtration prevents the discoloration and bad odor in the water.

When looking for a filter, find one that has these three processes because it will ensure that you have clean water at all times.

Flow rate

A good flow rate is a must-have in any filter. This water movement and the good flow rate is essential for keeping a clean and healthy environment for your fish.

Some filters have a flow rate adjuster. This adjuster is necessary as it gives you control over the amount of water flowing in the aquarium at a given time. You can adjust the water flow rate according to your specifications to promote growth and reproduction. An adjuster is not a necessity, but it won’t hurt to get a filter that has one.


You should also look at the size of the filter. You want to get one that does not occupy a lot of space and gives your fish enough swimming space. For this, you might have to consider the hang-on-back filters as they don’t take a lot of space. You can also get one that can be submerged; make sure this one is slim; however, so that it does not occupy a huge area.


You may have noticed that we talked about priming in some of the products. To get the most, you should look for a filter that self-primes. It will save you a lot of time as it works automatically after a power disruption or after cleaning. These are the best as they don’t require a lot of attention. Other filters lack this feature, but they make up for it by having priming buttons. Ensure that your filter has one of these two priming features.


For those of us who lead busy lives but love our fish, it is necessary to look for a filter that doesn’t require high maintenance. It should also be easy to assemble as this will save time once you are done cleaning. Also, look for one with a compact size as it will make your work that much easier.

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

It can benefit you greatly, knowing what types of filters there are and which ones are good for a 20-gallon aquarium. There are many types of filters, and these are some that work great with an aquarium of this size.

Undergravel Filter

As you can guess from the name, this filter is placed under gravel or substrate, which is the area that it will clean. It uses mechanical filtration by pulling the dirt and debris mechanically using the filter media. Some even use biological filtration that allows the good bacteria to grow for a cleaner aquarium.

Canister Filter

We have mentioned a product that is a canister filter. It is more durable and of higher quality than some of the other types of filters. It supports a three-stage filtration system, i.e., mechanical, chemical, and biological filtration. It has a siphon tube that filters the water while taking it inside the aquarium. It also has a separate tube that returns the water while at the same time controls the flow of the water. These features make this type of filter one of the pricier ones in the market.

Power Filter

Most of the products we reviewed are power filters. These are the most common ones, and they are also known as the HOB or hang on back filters. They are effective and give you versatility. This is because it includes the chemical, mechanical, and biological filtration processes.

Sponge filters

Though these are most common in 10-gallon aquariums, you can also find them in the 20-gallon ones. They are also called air-driven filters. They are the simplest and most efficient, especially great for hobbyists. These filters have an air pump that pulls water through sponge filters where mechanical filtration takes place, blocking out floating debris. The biological filtration happens on the sponge itself, where bacteria growth is promoted.

Internal filters

These are the filter types that are placed against the glass of the aquarium. They use underwater suction caps that capture the sinking waste before they get to the bottom. Some also use airlines and air pumps for the upwards water movement. This movement proves a good rhythm for biological, chemical, and mechanical filtration.

How to Install and Use the Filters

This is one of the most asked questions by aquarists. There are different aquarium filters, and here are some of the tips on how to install and use them.

Air-powered aquarium filter

These are the most common types of aquariums. These filters use an air pump to drive the filter. Water is drawn through the filter’s base and the media as the air bubbles rise.

When installing this filter, you have to make sure that it is below the water level. This should be done regardless of whether the filter is a sponge or one that sticks to the aquarium’s side. You have to install it below the water level to ensure that the air bubbles rise to draw the water through the media. Make sure the filter is positioned in a way that doesn’t allow the bubbles to be sucked into the filter’s intake tube.

It is also essential to install a check valve. It is a now-way valve that only allows air to pass through but stops water from back siphoning. Ensure that you fit the valve following the directions on the package.

Undergravel Filters

Undergravel filters are air-powered filters that use the same uplift principle as the air-powered filter. During installation, a perforated plate is placed in an empty aquarium, which is then covered with gravel. Uplift tubes are then connected to the plate; each tube has a porous air diffuser. You then connect the air pump to the diffuser once you fill the aquarium. Doing this will create a steady stream of bubbles. The bubbles cause a lifting effect, pulling the water in the aquarium into the gravel bed and away from the uplift tubes. This process aerates the water and enables water circulation.  

To keep the gravel bed clean, use a gravel siphon. To avoid backflow, mount the air pump above the aquarium or use check valves.

Hang On Back or HOB Power Filters

This filter is designed to hang on the back of the aquarium, as the name suggests. They use different types of filtration materials for particulate removal. These are easy to install as they take space behind the aquarium. You might have to cut out a section of a lid or light canopy if your aquarium has one to accommodate the filter. 

For those with open top aquariums, the filter can be hung anywhere on the back or the side. Always make sure you adjust the filter box level so that it doesn’t tip backward; this is because the pump is continually filling. You need to make sure you always keep the filter cartridge clean to avoid back –up which may lead to spills.

One important thing to note is that you should fill the aquarium before starting the pump to enable the initial priming.

Internal Power Filters

This filter design is fully submersible. The motor, filter box, and cartridge are submerged. It cleans by recirculating water through the filter cartridge then back to the tank. The filters use suction cups or clips that hang on the tank’s side. This filter has an adjustment valve that lets you control the number of bubbles. And just to emphasize on the installation; it is done by completely submerging the filter in the aquarium water. 

Canister Filters

Canister filters use multiple stages of chemical, biological, and mechanical filtration. Water flows due to gravity into the filter media. The canister filter has an inlet and a return hose. The inlet hose uses gravity to bring the water to the canister filter; the water is then filtered and is pumped back to the tank using the return hose. The canister has a water pump built into it that takes the purified water back to the aquarium. Installing the canister filter is easy but needs a little planning. Make sure to get the various filter media in the correct position for it to work correctly.

How to Clean and Maintain

For the filters to work correctly, they need frequent cleaning. How do you know when it’s time to clean your filter? Filters should be cleaned regularly to avoid clogging. You can, however, wait for a week or two to allow your fish to get used to the new environment before changing it again.

How to clean a mechanical filter

Mechanical filters have a sponge or a pad that does the cleaning, and that is what you will need to clean. To do so, use the water that is already in the tank. Put some water in a bowl, unplug the filter to avoid getting shocked then clean the sponge using the water and your hands. Squeeze the sponge to remove excess dirt. Then use the remaining water to scrub the casing and the tubes using a cleaning brush. After all, is said and done, put the pad or sponge back and turn the filter back on.

Cleaning chemical filters

When cleaning a chemical filter, all you have to do is to swap out the carbon regularly. Remove the carbon before you remove the water and replace it before reattaching the filter.

Cleaning biological filters

This should not be done as regularly as the other filters. Just clean it once in a while using the same water in the aquarium. Make sure to unplug the filter before you start, then scrub the casings and put it back once you’re done


Q: What are the most trusted 20-gallon aquarium filter brands?

A: There are many of these filters, but if you want quality, I would suggest using brands like Marina, MarineLand, Aqueon and of course the most trusted of all brands

Q: What size of filter do I need for my 20-gallon tank?

A: According to manufacturers, the size of the filter will depend on the size of the tank. For a 20 gallon tank, it would be safer to go with those that say “up to 20 gallons” or “up to 30 gallons”. These are the maximum sizes that you can install in your aquarium.

Q: Can I use a 20-gallon filter for a 30, 40, 50-gallon tank?

A: You can only use a 20-gallon filter for a 20-gallon tank or less. Using the same filter on larger tanks might work but will take a lot of time to filter. It is advisable to use the correct measurements for easier cleaning.

Final Words

This has been a long article, but we finally made it to the end. It is long because I wanted to make sure that you get the best available filters for your tank. It can be a hard task to do, and I hope this article has helped simplify the process. You might find that the filters may behave differently on your aquarium than in others, but don’t let that worry you, not all experiences can be the same. Always remember to read instructions carefully and follow them to the T. This way, you will get the best results with maximum efficiency. Take care of your filter, and this, in turn, will help take care of your fish. Happy cleaning!

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