8 Best Aquarium Filters In 2021

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This is our review of the best aquarium filters of 2021.

After reviewing and testing dozens of aquarium filters, I’ve found the Fluval FX6 to be the best overall aquarium filter of 2021.

I have a history with almost all the aquarium filters on this list, so I applied what I knew about them, along with the knowledge of others to make educated choices for the aquarium filters on this list so you can make the best possible decision for your tank.

The Fluval FX6 passed all of my tests, from having biological filtration to adjustable flow rates.

However I understand that your needs may differ from what the Fluval FX6 has to offer, so I reviewed other aquarium filters that offer similar or unique benefits.

Let’s get started.

Our Best Aquarium Filters

  1. Fluval FX6 (Best Canister Filter)
  2. Tetra Whisper EX (Best Small Tank Filter)
  3. Aquaclear Hagen Power Filter (Best Power Filter)
  4. Penn Plax Premium Undergravel Filter (Best Gravel Filter)
  5. Fluval U4 Underwater Filter (Best Internal Filter)
  6. Marineland Penguin Bio-Wheel Power Filter
  7. Tetra Whisper IQ Power Filter
  8. Fluval C3 Power Filter

Fluval FX6 

(Best Canister Filter)

For those of you wanting a high quality professional grade aquarium filter made for large tanks up to 400 gallons, then the Fluval FX6 is a great option to consider.

This filter is packed with so many features that I couldn’t even name all of them off the top of my head.

One of my favorite parts of the FX6 is that it’s self-primed and practically leak-proof, which is a huge plus for preventing water runoffs!

Above that, this filter is designed with stackable media brackets, allowing you to customize the filter media. This means that you’ll have the full ability to easily adjust what you’re filtering for, making filtering easier and more powerful.

Built into the basket are seals that prevent water from bypassing out. The auto stop valves also help prevent water from leaking or back flowing into your aquarium as well. Basically, water will have a heck of time trying to escape!

So if you’re looking for the best filter available, consider the Fluval FX6.

Pros
  • Professional grade filter
  • Filters up to 400 gallon tanks
  • Self-primed
  • Stackable media baskets
  • Multiple auto stop water valves
Cons
  • Cost
  • Not the best for smaller tanks

Tetra Whisper EX

(Best Small Tank Filter)

When it comes to filters for small tanks, the Tetra Whisper EX is a match made in heaven.

Designed for quietness, the Tetra Whisper EX is ideal for freshwater tanks that don’t require the power of something large like a 125 gallon reef tank.

This Hang On Back(HOB) filter requires very little effort to install on your end. Essentially, you just hook the bad boy to the back of your aquarium and let it get to work.

Performance wise, the media inside this filtration system is designed to help beneficial bacteria grow and thrive throughout the tank. This is important in cycling, and maintaining healthy aquarium waters inside your tank.

My favorite part of this filter is how quiet it is. Compared to other filters out there with loud motors, the only thing you’ll hear from this filter is a faint trickle of water.

So if you have a small tank and are looking for a small, yet powerful filter, the Tetra Whisper EX checks all of our boxes!

Pros
  • Quiet
  • Easy to setup and use
  • Filter media allow beneficial bacteria to grow
  • Reliable and powerful
  • Low maintenance
Cons
  • Not the best for saltwater tanks

AquaClear Hagen Power Filter

(Best Power Filter)

For those wanting a quiet power filter that gets the job done, the AquaClear Hagen Power Filter is the option for you.

This filter is the quietest on the list, and one of the least-noisy aquarium filters I’ve ever used. The reason it’s so quiet is because it lacks a “bio-wheel”, meaning water isn’t splashing around as much.

Don’t let its quietness fool you into thinking it’s weak though, as this bad boy can filter up to 100 gallon aquariums! 

Besides it being so quiet, another thing I like about this filter is its adjustable flow rate, making it suitable for keeping delicate fish and shrimp. It also has a two-year warranty, which is a nice safety measure to have.

So if you’re looking for a quiet, reliable, and powerful aquarium filter, the AquaClear Hagen Power Filter may be for you!

Pros
  • Extremely quiet
  • Adjustable flow rate
  • 3 stage filtration
  • Filters up to 100 gallon aquariums
Cons
  • Box design allows lots of water to pass through the biological stage quickly.
  • May need additional filtration for larger tanks.

Penn Plax Premium Undergravel Filter

(Best Gravel Filter)

Whether you want to use a gravel filter for its planted aquarium benefits, or like the functions they offer, the Penn Plax Premium Undergravel Filter is among the best of the undergravel filters available.

These puppies are easy to set up. Simply bury the filter under the aquarium substrate, add an air pump for power, and your filter should be up and running!

One problem with undergravel filters is that they leave debris in your substrate. However, planted aquariums shouldn’t have this issue as much. For that reason, you should really only use an undergravel filter if you have a planted aquarium.

In general, this filter provides enough filtration and circulation in the tank, keeping your plants healthy and happy!

Whether you have a planted aquarium, or are in the market for a gravel filter for another reason, the Penn Plax Premium Undergravel Filter is the option for you!

Pros
  • Easy to setup and use
  • 2 stage filtration
  • Entire bottom of tank is filtered
  • Little to no maintenance
Cons
  • Leaves debris in substrate
  • Not the best option for non-planted tanks.

Fluval U4 Underwater Filter

(Best Internal Filter)

If you’re looking for a highly effective and compact internal filter, then look no further than the Fluval U4 Underwater Filter.

This filter boasts three stage filtration, coming with a poly/carbon cartridge, foam pad, and Biomax ceramic media. Making this filter ideal for freshwater, marine, and reptile aquariums.

This filter also has a three way flow control feature allowing you to change the water output position, creating an ideal flow in your aquarium.

Another nice thing about this baby is that it can be installed either horizontally or vertically, making it usable for almost all tank shapes and sizes.

So If you’re in the market for a flexible, effective, and compact internal filter to get the job done, the Fluval U4 Underwater Filter may be for you.

Pros
  • 3 stage filtration
  • 3 way flow control feature
  • Can be installed either horizontally or vertically
  • Easy to use and setup
Cons
  • None

Marineland Penguin Bio-Wheel Power Filter

Simple, reliable, and extremely effective, the Marineland Penguin Bio-Wheel Power Filter is a great option for tanks of all sizes!

Coming in different variants, this filter can handle anything from a 5 gallon nano tank to a large 75 gallon aquarium.  

The best part of this filter is its dual wet/dry bio-wheel which increases the growth of beneficial bacteria inside your tank. Resulting in cleaner and safer water for your fish.

From what I’ve seen using this filter myself, it seems to be extremely durable as I haven’t had problems with it since I purchased it. Making it a great long term solution to filtering your tank.

The only thing I don’t like about this filter however, is that you need to buy Marineland filter cartridges for it to run its best. 

However, its high flow rate, efficient filtration system, and dual bio-wheel make up for this.

Overall, the Marineland Penguin Bio-Wheel Power Filter is a great option for filtering your tank!

Pros
  • 3 stage filtration
  • High flow rate
  • Efficient filtration
  • Easy to setup and use
Cons
  • Needs Marineland filter cartridges to run best

Tetra Whisper IQ Power Filter

For those looking for something simple and convenient, the Tetra Whisper IQ Power Filter is a great option to consider.

Coming with Bio-Bag filter cartridges, replacing your old filter with this one will be as simple as stealing candy from a baby. Simply take the old filter out, put the Tetra Whisper inside the tank, and you’re good to go!

As its name suggests, this aquarium filter won’t make a lot of noise. In fact, sometimes I don’t even hear the filter. It’s REALLY quiet!

So if you’re looking for a simple, effective, and quiet filter for your aquarium, look no further than the Tetra Whisper IQ Power Filter.

Pros
  • Quiet
  • Simple and easy to use
  • Comes with Bio-Bag filter cartridges
  • Great for freshwater tanks
Cons
  • Comes with low quality filter media.

Fluval C3 Power Filter 

Last but not least, the final item on our list of the best aquarium filters is the Fluval C3 Power Filter.

This puppy boasts 5 stage filtration, ensuring that your water is clean and crystal clear.

Made for both freshwater and saltwater aquariums, this filter can be used in almost any fish tank setup

Compared to other power filters out there, the Fluval C3 isnt that loud. Although you may hear a humming motor at times, this bad boy is pretty quiet for its size.

Overall, the Fluval C3 Power Filter is a great option for both freshwater and saltwater tanks!

Pros
  • 5 stage filtration
  • Made for both freshwater and saltwater aquariums
  • Quiet
  • Easy to setup and use
  • Beginner friendly
Cons
  • Motor sometimes hums

What To Look For When Buying An Aquarium Filter

When purchasing an aquarium filter, it’s important to know what makes one high quality. There are 4 different aspects that make a high quality aquarium filter, those are:

  • The Filter Matches Your Aquarium Size
  • The Filter Can Handle The Fish Population
  • The Filter Has A Good Flow Rate
  • The Filter Has Good, Reliable Technology

The Filter Matches Your Aquarium Size

One of the most important requirements for an aquarium filter is that it’s built for your aquarium size. You shouldn’t buy a large filter for a small tank, or a small filter for a large tank.

The reason for this is because too much or too little power can stress your fish.

Instead, make sure your aquarium falls into the recommended tank size on the filter you plan on buying.

The Filter Can Handle The Fish Population

The health and safety of your fish should be the main priority of your tank. As you introduce more and more fish into the aquarium, more ammonia and other toxins are released into the water through your fish.

With that, it’s important that your filter can handle cleaning the water of 5, 10, or even 20 fish! If your filter cannot handle picking up after a community of fish, this can cause them to become stressed and possibly die early.

The Filter Has A Good Flow Rate

One of the most important aspects of an aquarium filter is its flow rate. Generally, you can find a filter’s flow rate by looking at its GPH(Gallons per hour) metric. This will tell you how many gallons of water your aquarium filter will process every hour.

For example, let’s say that a filter has a 60 GPH. That means that the aquarium filter will filter through 60 gallons of water every hour. 

So how much GPH should your aquarium filter have?

The rule of thumb is to have a GPH of 3-5 per gallon of water inside your tank. That means if you have a 20 gallon aquarium, your filter should have 60-100 GPH.

Here’s a table for reference:

Aquarium Size in GallonsRecommended GPH
10 Gallons30-50 GPH
20 Gallons60-100 GPH
40 Gallons120-200 GPH
70 Gallons210-350 GPH
100 Gallons300-500 GPH
125 Gallons375-625 GPH

The Filter Has Good, Reliable Technology

When choosing the best aquarium filter, picking the newest or most advanced model isn’t always the best choice. Instead, look for good, yet reliable features

Let me explain.

Many advanced and feature intensive aquarium filters tend to burn or die out faster. The reason for this is because fancier and more advanced filtration systems require more complex processes than a basic simple filter, which increases the risk of something going wrong. The gears in a new filter may burn out. The collision detection system may cause a spark in voltage in the water. You get the point.

Therefore, instead of looking for the newest and most innovative filter available, I look for proven systems that have already stood the test of time in tanks around the world. 

A good, basic filter can often perform at the same or even better level than a filter packed with all the features you could ever want.

Focusing on a simple, yet reliable filter system is always a good idea!

Different Types Of Aquarium Filters

There are numerous different types of aquarium filters, it’s important you understand each one before making your decision on which filter you want.

Here are the 5 main types of filters:

  • Power Filters
  • Canister Filters
  • Internal Filters
  • Wet/Dry Filters (Sumps)
  • Undergravel Filters

Power Filters

Also known as Hang On Back(HOB) filters, power filters are one of the most popular types of aquarium filters on the market.

They’re known for their quiet, self-enclosed nature, and hang on the wall of your aquarium, making them easy to maintain and use.

Canister Filters

Located on the outside of your tank, canister filters are generally used in larger tanks that require a more powerful filter.

They run on multiple different filter media, making them a powerful, yet reliable filter option for most tanks.

They are also useful for tank owners that wish to not have a bulky filter blocking part of their aquarium.

Internal Filters

Internal filters sit in the corner of your tank and are powered by a pump that can run on either water or air.

The pump sucks the water through a sponge where beneficial bacteria live. This bio-filter setup allows the water to become free from toxic chemicals like ammonia and nitrites. 

This basic filter setup is generally used in very small aquariums without many fish, as the power output isn’t as strong as other types of aquarium filters like canister filters. 

Wet/Dry Filters (Sumps)

Wet/Dry (Sump) filters are unique, as they are one of the only filter types that have multiple compartments that you can fill with different types of media. 

These filters allow you to “ultra filter” your water without having to buy something as powerful as a canister filter.

Undergravel Filter

Last but not least, the last type of filter is the undergravel filter.

These filters sit along the bottom of your aquarium, under the substrate. With that, you’ll have to install these bad boys when you’re setting up the tank.

Gravel filters are useful, as they help create a current and clean the substrate along with cleaning the water.

How Do Filters Work

So how exactly do filters clean and purify your water? Well there’s three steps a filter goes through when cleaning the water, those are:

  • Step 1: Mechanical Filtration
  • Step 2: Biological Filtration
  • Step 3: Chemical Filtration

Step 1: Mechanical Filtration

The first step in the process is the mechanical filtration stage.

At this stage, your filter mechanically removes debris from the water it’s stucking in through a fine mesh or wadding of cotton, called the filter pad or sponge filter.

Essentially, it’s collecting all of the clunky stuff from the water and storing it in a place out of reach from the tank.

Step 2: Biological Filtration

After your tank has collected the clunky stuff from the water, your filter now has to collect the dirty chemicals from the water.


To do this, your filter develops a layer of beneficial bacteria to eat away at the chemicals plaguing the tank.

This process is known as the nitrogen cycle, and it’s where your filter transforms ammonia and nitrites into a safer chemical known as nitrate.

Step 3: Chemical Filtration

After your water has passed through the mechanical and biological filtration, it then has to be chemically neutralized using either an activated carbon media or a resin before heading out back into the tank.

Filter media usually sit in a bag, cartridge, or internal basket inside your filter, allowing the water to be cleansed throughout the whole filtering process.

During the chemical filtration process, your water is essentially purified, getting ready to head back into the aquarium.

Aquarium Filter FAQ

Whether you’ve already purchased, or plan on purchasing an aquarium filter, you may have some questions come up in your mind. Here are some of the most common questions I get about aquarium filters.

How Do I Clean An Aquarium Filter?

Giving a default procedure to clean an aquarium filter is difficult as each filter is different.

When cleaning an aquarium filter though, there’s a couple things you don’t want to do. The first of which being to NEVER CLEAN YOUR FILTER UNDER THE TAP! 

The reason for this is because tap water contains chlorine, and chlorine will exterminate all the beneficial bacteria inside the filter. And without that bacteria, your filter won’t do nearly a good job as it should.

The second thing you don’t want to do is fully clean the filter. Although it’s  important to not slack during the cleaning process, it’s even more important to not wipe out all the bacteria from the filter completely.

And finally, the third thing you shouldn’t do is USE SOAP, as soap will seep into your tank through the filter.

For finding an exact tutorial on cleaning your aquarium filter, I personally recommended checking on YouTube for the model of the filter you have.

How Often Should I Clean My Aquarium Filter?

My personal advice is to clean the filter every 3 weeks. I’ve personally found this to be the sweet spot in the majority of my aquariums.

However, this is just a piece of advice, and not a definite rule. The real answer is to clean your filter when it gets dirty!

Most importantly though, make sure you clean the filter a week after you’ve done any other type of tank maintenance, such as performing a water change or any other change to the environment.

One definite rule of thumb I can give is to replace the activated carbon inside the filter every month, and the foam filter insert every two months.

How Do I Reduce The Flow You My Aquarium?

One of my favorite ways to reduce the flow of an aquarium filter is to insert a spray bar. A spray bar will distribute the water through tiny holes along a tube, which will create a clamer current for your aquarium.

Another thing I like to do is raise the height of my filter, however you’ll have to be cautious of water splashing out of your aquarium if the filter gets too high.

Along with that, many filters on this list will come with flow control, which will allow you to control the flow of the filter without having to modify the height of the filter or do anything else.

Do Small Tanks Need An Aquarium Filter?

Yes, all tanks need a good aquarium filter. However, if your tank is less than 10 gallons, you could possibly get away without using an aquarium filter.


If you do decide to not use an aquarium filter, make sure that the ammonia and nitrite levels inside the tank are low to ensure your fish stay happy and healthy.

However, it’s better to be safe than sorry, so I recommend you ALWAYS have some type of filter in your tank.

Our Verdict

A great aquarium filter is one that is reliable, matches your aquariums needs, and has an adjustable flow rate.

Brownie points if it has 3 stage filtration!

With that, the Fluval FX6 passes all of our tests, making it the best aquarium filter of 2021!

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Author
Hey there, my name is Gunnar Kennedy. I'm a fishkeeping enthusiast who's been in the hobby for over a decade now! I love sharing new ideas and helping others care for their aquatic friends!

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