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The Best Small Aquarium Filter For Small And Nano Tanks

Whether you’re looking for a compact internal filter for your nano tank, or an external canister for a small tank, check out our guide to help find the best small aquarium filter for you!

By Matt Thomas
Last updated on

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best small aquarium filter

Choosing the best small aquarium filter can be a balance between finding one that’s efficient and powerful enough to give you crystal clear water, but that’s also compact enough to fit in your tank!

We’ve reviewed and assessed some of the best small aquarium filters, and found that the best option for a small nano tank is the Tetra Whisper Internal Filter for it’s powerful flow and efficient cleaning in a great compact size.

But we’ve also covered a range of hang on back (HOB) and external canister filters to suit both small and mid-size tanks. So whatever size of small aquarium you own you’ll find the right filter here.

Let’s take a look at the list!

  1. Best For Nano Tank: Tetra Whisper Internal Filter
  2. Best For Value: Marineland Penguin 100 Filter
  3. Quietest HOB: AquaClear 20 Power Fish Tank Filter
  4. Best Premium Canister: Fluval 107 External Filter
  5. Best Alternative Canister: Penn Plax Cascade 500 Filter
  6. Best For Budget: Aqua-Tech Power Aquarium Filter
  7. Best Slimline HOB: Marina S10 Power Filter
  8. Best For Easy Maintenance: Tetra Whisper EX20 Power Filter

Best Small Aquarium Filter Picks Reviewed

When considering the best small aquarium filter it’s important to do your research and understand the features you need for your specific tank. From capacity to media type, to flow rate we’ve covered all this and more to help you make the right choice.

1. Tetra Whisper Internal Filter


  • Filter Type: Internal
  • Dimensions: 3.0 (w) x 3.0 (d) x 7.38 (h) inches
  • Flow Rate & Aquarium Capacity: 27 GPH, for tanks up to 4 gallons (other sizes available)
  • Filter Media: Whisper Bio-bag with 3 stage filtration
  • Best For: Nano Tank

The Tetra Whisper Internal Filter is a powerful but compact mini filter designed for nano aquariums up to 4 gallons. Its 3.0 x 3.0 x 7.3 inch size and convenient tank clip means you can easily position it in the corner of a small tank without it taking up too much space.

With a flow rate of 27 GPH, it can cycle all the water in a 4 gallon tank almost 7 times per hour – plenty for a tank that size. Although if you have small fish or ones with delicate fins do cover the intake with filter mesh to avoid any accidents or them being sucked in.

The 3 stage Whisper Bio-bags are really easy to change too. You just flip up the hinged lid and slot in a new cartridge. Each one contains fiber to catch debris and allow bacteria to colonize, while activated carbon provides chemical filtration to keep your water safe for your fish.

Many owners report this is a quiet, but powerful filter and its air pump also helps to oxygenate the water to keep their fish healthy. A great internal filter for a small aquarium!

2. Marineland Penguin 100 Filter

Marineland Penguin 100 Hang On Back Filter


  • Filter Type: Hang On Back
  • Dimensions: 5.5 (w) x 5.5 (d) x 8.0 (h) inches
  • Flow Rate & Aquarium Capacity: 100 GPH, for 10 to 20 gallon tanks (other sizes available)
  • Filter Media: 3 stage filtration consisting of Rite-Size A cartridge (mechanical, chemical) and bio-wheel for wet/ dry filtration
  • Best For: Value

If you’re on a budget but want an efficient hang on back filter for a 10 to 20 gallon aquarium, the Marineland Penguin 100 is a great choice. At 5.5 x 5.5 x 8.0 inches it’s a fraction deeper than some HOB filters, but you also have the smaller Penguin 75 for tanks under 10 gallons.

Mechanical and chemical filtration are provided by Marineland’s Rite Size A cartridge. It’s great for removing small particles, but watch for larger debris at the intake hose when you do your weekly clean. And the activated carbon is fantastic at removing toxic ammonia and nitrates.

But it’s the Bio-wheel, providing biological filtration, that really adds to this filter. Because the bio-wheel spins contacting the air and water, it allows beneficial bacteria to colonize more efficiently. And more of this bacteria thriving and breaking down toxins means a cleaner tank.

Overall, even with the bio-wheel spinning, owners of this filter praise it for being quiet and really easy to maintain.

3. AquaClear 20 Power Fish Tank Filter

AquaClear 20 Hang On Back Filter


  • Filter Type: Hang On Back
  • Dimensions: 5.0 (w) x 4.0 (d) x 6.25 (h) inches
  • Flow Rate & Aquarium Capacity: 100 GPH, for 5 to 20 gallon tanks (other sizes available)
  • Filter Media: 3 stage filtration – foam for mechanical, carbon for chemical, and BioMax rings for biological filtration
  • Best For: Quietest HOB

AquaClear HOB filters are some of the quietest hang on back filters given the power they provide. The AquaClear 20 is designed for 5 to 20 gallon tanks, and we found it perfect for tanks of this size.

Its 5.0 x 4.0 x 6.25 inch size is very compact for a 10 gallon tank, especially considering most of the unit hangs off the back. And the 100 GPH flow rate is fully adjustable down to around 33 GPH, making it great for fish with delicate fins.

One of the great things about this filter, which many owners agree with, is the ability to access and customize the media. There’s plenty of room to add your own media, although the Activated Carbon and BioMax rings supplied do a great job of removing ammonia and toxins.

Overall a super quiet and efficient hang on back filter for your small aquarium that’s really easy to customize and maintain too!

4. Fluval 107 External Filter


  • Filter Type: Canister
  • Dimensions: 7.5 (w) x 7.0 (d) x 13.7 (h) inches
  • Flow Rate & Aquarium Capacity: 145 GPH, for 10 to 30 gallon tanks (other sizes available)
  • Filter Media: Fully customizable media baskets, includes 2 x Bio-Foam Max, 2 x BioFoam, BioFoam+, Carbon, and mechanical Quick Clear particles
  • Best For: Premium Canister

Our pick for the best small canister filter is the Fluval 107. Whilst it’s a premium filter, and that’s reflected in the price, because it’s external it means it won’t take up any space in your small fish tank. Having said that, at 7.5 x 7.0 x 13.7 inches it’s pretty compact for an external filter too.

Its 145 GPH flow rate is fully adjustable and can cycle a 20 gallon aquarium over 7 times an hour, which is plenty to keep your water crystal clear. It also has 4 filtration chambers and you can completely customize them with mechanical, chemical and biological media to remove all the waste in your tank.

Maintenance is made really easy with the AquaStop valves, allowing you to disconnect and clean the unit while leaving the tubes inside your tank. And the quick primer makes restarting the unit simple.

Overall this is a fantastic canister filter, which owners praise for being incredibly quiet and leaving their water clear with just a few hours of use.

5. Penn Plax Cascade 500 Filter

Penn Plax Cascade 500 Canister Filter


  • Filter Type: Canister
  • Dimensions: 11.5 (w) x 9.0 (d) x 13.5 (h) inches
  • Flow Rate & Aquarium Capacity: 115 GPH, for tanks up to 30 gallons (other sizes available)
  • Filter Media: 2 fully customizable media baskets, includes 2 Poly Fiber Floss Pads, 1 Coarse Bio-Sponge, and 1 Bag of Activated Carbon
  • Best For: Alternative Canister

An awesome alternative to the Fluval 107 is the Penn Plax Cascade 500 canister filter. With its 115 GPH flow rate it can cycle a 20 gallon aquarium just under 6 times an hour which is perfect for a tank that size.

The large customizable media baskets allow you to add your choice of mechanical, chemical and biological filtration media so you can get your water clear and toxin free. 

It comes with poly fiber pads which are great at removing debris, activated carbon and bio-sponge. Although we prefer bio-rings for more surface area for bacteria, the bio-sponge still works really well and you can easily replace it.

Many owners give this filter great praise for its large capacity, easy to use push-button primer and accessories such as the aerating spray bar, which helps to further oxygenate the water and provide a healthy tank for your fish.

6. Aqua-Tech Power Aquarium Filter


  • Filter Type: Hang On Back
  • Dimensions: 5.19 (w) x 4.88 (d) x 7.63 (h) inches
  • Flow Rate & Aquarium Capacity: 90 GPH, for 5 to 15 gallon aquariums (other sizes available)
  • Filter Media: 3 stage filtration. Includes AQUA-Tech EZ-Change Filter Cartridge with polyfiber pad for mechanical, activated carbon for chemical and BIO-Fiber for biological filtration
  • Best For: Value

Another great value hang on back filter is the Aqua-Tech Power Aquarium Filter. It’s suitable for 5 to 15 gallon aquariums. And with a width of 5.19 and depth of 4.88 inches it hardly takes up any room in your small aquarium, especially as most of the unit sits outside the tank.

The 90 GPH flow rate can fully cycle a 15 gallon aquarium up to 6 times an hour, which is at the higher end of the recommended minimum range, so will help keep your water clean and clear. And there’s just enough space in the filter chamber to customize with your own media.

Having said that, it comes with an AQUA-Tech EZ-Change Filter Cartridge which has coarse floss to filter debris, a carbon chemical filtration layer, and Bio-Tech grid with extra surface area for beneficial bacteria to colonize, giving you super clear water.

Overall, this is a fantastic little filter for the price and many owners report it’s quiet, easy to use, and gets your water nice and clear.

7. Marina S10 Power Filter

Marina S10 Hang On Back Filter


  • Filter Type: Hang On Back
  • Dimensions: 6.50 (w) x 3.70 (d) x 7.30 (h) inches
  • Flow Rate & Aquarium Capacity: 55 GPH, for tanks up to 10 gallons (other sizes available)
  • Filter Media: Bio-Carb Cartridge for mechanical and biological, Bio-Clear Zeolite Cartridge for chemical filtration (sold separately)
  • Best For: Slimline HOB

If you want a compact HOB filter for your small fish tank then the Marina S10 Power Filter is definitely worth considering. The S10 is one in a range of different sizes, and is suitable for a tank up to 10 gallons, although we found the S15 Power filter even better for 10 to 15 gallons.

Its slim profile is 3.70 inches deep meaning it only protrudes about 2 inches from the back of your tank. Perfect if you have limited space and want to get your small aquarium closer to the wall.

The 55 GPH flow rate can cycle a 5 gallon tank up to 11 times an hour, which is great for overfiltering your water. But it’s also fully adjustable making it suitable for delicate fish like bettas. And the pre-filter sponge over the intake helps make sure your fish can’t get sucked in.

Marina produce various filter cartridges including Bio-Carb filters with activated carbon and Ceramitek which helps colonize beneficial bacteria, and Bio-Clear cartridges containing zeolite which absorbs ammonia well. These work together to give you ultra-clear water in your tank.

Overall this is a fantastic slimline filter which many owners report is quiet and great for customizing if you want to add your own media too!

8. Tetra Whisper EX20 Power Filter

Tetra Whisper EX20 Hang On Back Filter


  • Filter Type: Hang On Back
  • Dimensions: 6.06 (w) x 5.56 (d) x 9.19 (h) inches
  • Flow Rate & Aquarium Capacity: 110 GPH, for 10 to 20 gallon tanks (other sizes available)
  • Filter Media: 3 stage filtration provided by Bio Scrubber (biological) and Tetra EX Carbon Filters (mechanical and chemical)
  • Best For: Easy Maintenance

The Tetra Whisper EX20 Power Filter is one of the easiest filters to set up and maintain and is designed for tanks between 10 and 20 gallons. It’s 6.06 x 5.56 x 9.19 inch size means it won’t take up much space in your tank considering the main unit hangs off the back.

Biological filtration is provided by a Bio Scrubber layer designed to never need replacing. You simply remove and rinse the layer with tank water around once a month. The Bio Scrubber allows beneficial bacteria to grow on it and removes ammonia and nitrites from the water.

It also uses medium size Tetra EX Carbon Filters which are really easy to change. These contain a coarse floss layer and finer layer to remove particles, along with activated carbon to remove toxins keeping the water safe for your fish and removing any smells.

One thing to note with this filter is that the flow is not adjustable but in a tank between 10 to 20 gallons it’s a good cycle rate. Overall many owners praise this filter for being quiet, effective and really easy to maintain.

Why Do Small Aquariums Need A Filter?

small aquarium on table

Maintaining the right water conditions to keep your fish happy and healthy becomes all the more challenging in a small aquarium. This is particularly true for nano aquariums (whilst there’s no official definition of a nano aquarium’s size, most aquarists consider it to be 10 gallons or less).

The smaller water volume means harmful toxins such as ammonia can build up much quicker than in a larger tank. In addition to managing this through regular water changes, it also means the right filter is a critical piece of equipment for a small fish tank.

And not only do you need one that has the right amount of power and will provide the right filtration, but it also needs to be small enough to fit in your tank! 

So let’s start by looking at how filter media actually filters your water.

Small Aquarium Filter Media

The majority of filters, are known as ‘3 stage’, meaning they contain three types of media. As the water is pumped through the filter, the filter media works together to cleanse it and remove toxins to help your water parameters stay at the right levels.

Mechanical Filtration

The first media layer in your filter tends to be mechanical. Simply put it’s a physical filtration media, often of sponge or fiber bundles, that captures larger debris and particles from the water.

To maintain your filter properly it’s usually this layer that needs the most attention. You should check your mechanical media on a weekly basis in case any obvious debris needs removing, and most will need replacing around once a month. 

Biological Filtration

Often the second layer of filtration, but arguably the most important, biological filtration supports your tank’s nitrogen cycle. Beneficial bacteria colonize the media and break down harmful ammonia from excess food and fish waste into nitrite, and then less harmful nitrate.

You should test your small aquarium’s water parameters at least once a week. Ammonia levels should never be higher than 0.1 ppm [1], but in a small or nano aquarium it’s particularly important to have them as close to 0 as possible. And biological filtration will help with that!

Chemical Filtration

This filter media often contains substances like activated carbon or zeolites [2], which help to absorb ammonia and other toxins from the water. Note that these substances don’t last forever and you’ll probably need to change out your chemical media every month or so.

Best Types Of Small Aquarium Filter

The best small aquarium filters need to fit your tank without taking up too much space, have the right flow rate to effectively cycle your water, and have 3 stage filtration as discussed above.

  • Hang On Back (HOB) Filters: One of the most common types of small aquarium filter, HOB or power filters have a body that hangs outside your tank. A siphon sucks up water, runs it through the filter media and the water then cascades back into your tank.
  • Internal Filters: These are great for tanks under 20 gallons. But as they sit inside they do take up space, so make sure you get a suitable size. Most use all three mechanical, biological, and chemical stages providing great filtration for a small tank.
  • Canister Filters: Whilst these filters are usually used for larger fish tanks, you can get many suitable for small aquariums too. As they are external they don’t take up any space in your tank, and you can customize the 3 stage media easily. Many aquarists choose to increase the bio media, for example, to house more beneficial bacteria. They are also one of the quietest aquarium filters to run.
  • Sponge Filters: One of the simplest types, these filters use air driven through the sponge material to clean the water. They are good for a small aquarium or for nano fish where the bioload is low. The sponge mainly performs mechanical filtration by capturing debris, and some biological filtration via bacteria living on it.

Undergravel filters are another option, although we wouldn’t necessarily say they were the best small aquarium filter. They can be great as a betta tank filter as they hardly produce any current, but your gravel will need siphoning regularly.

purple and white betta fish

How To Choose The Best Small Aquarium Filter

When choosing the best small aquarium filter for your tank you’ll need to consider factors including capacity and flow rate. Let’s look at the main things to think about.

Aquarium Size And Filter Capacity

The size of your tank is a key factor in choosing the best small aquarium filter, not only for the volume of water it can handle but also its physical size. Whilst there are no set rules, the following options can work well:

  • Up To 5 Gallon Aquarium: Small internal filters are often good for nano tanks of this size, with many of them having built-in internal filtration. Smaller HOB filters can sometimes be a good option too.
  • 5 to 10 Gallon Aquarium: Again, you’ll often see many HOB and internal filters for tanks of this size, and many manufacturers make multiple sizes of the same model. 
  • 10 to 20 Gallon Aquarium: In addition to HOB and internal filters being a common choice for tanks this size, smaller canister filters are available too. And because they are external they won’t take up room in the tank.

Filter media and capacity is also a consideration here. Many smaller internal and HOB filters use all-in-one filter pads for example, that are still able to perform 3 stage filtration but make maintenance much easier.

Filter Flow Rate

Arguably one of the most important factors when considering the best small aquarium filter for your tank is its flow rate (also known as turnover). In fact, it’s the flow rate that manufacturers use to show what size tank each filter is recommended for.

Flow rate is measured in gallons per hour (GPH), and as a general rule most freshwater aquarists recommend your filter should be able to cycle all the water in your tank at least 4 to 6 times per hour. So for a 10 gallon tank you’d want a 40 to 60 GPH filter.

Having said that, overfiltering is always a good idea, particularly if you have a well populated tank. So I’d always opt for a filter at the higher end of this range, or even over it. The key is never to have a flow rate that’s too low for your tank size.

Consider Your Fish

It’s important to think about your fish when choosing your aquarium filter too. The best small aquarium filter for your fish can vary depending on their species. If you own a betta fish, for example, choose a filter with an adjustable flow rate as they don’t do well with a strong current.

On the other hand, if your small aquarium is well stocked with nano fish that produce a lot of waste, you may want to opt for a more powerful filter that can handle the high bioload. Both HOB and internal filters are good options, but it is worth researching the needs of your fish.

Pre-Filters And Additional Factors

Another consideration when it comes to your fish, particularly in a small aquarium, is the use of a pre-filter. Pre-filters are simply safety barriers that fit over your filter intake to stop small fish, shrimp or fry being sucked in. You can often make your own using filter sponge.

Finally, when looking for the best small aquarium filter, take some time to consider how easy it is to maintain and how quiet it is. Internal filters and HOBs are often easy to clean with replaceable pads, while canister filters can be some of the quietest.

Our Verdict

If you need an efficient yet compact filter for a nano aquarium, the Tetra Whisper Internal Filter is one of the best options available. Or another way of saving space in a small fish tank is a slimline hang on back (HOB) like the Marina S10 Power Filter.

Or if you prefer an external filter for a slightly larger 10 to 30 gallon tank, the Fluval 107 External Filter is an excellent choice that allows you to fully adjust the flow rate, gives plenty of room for customization with your own media, and gives you crystal clear water.

But when it comes to choosing the best small aquarium filter for your tank there are plenty of alternatives here on our list too!


Find out the answers to some of the most frequently asked questions about choosing the best small aquarium filter for your tank below.

What Flow Rate Should My Filter Have?

Your filter should be able to cycle all the water in your aquarium a minimum of 4 to 6 times an hour. So for a 5 gallon tank that would be a 20 to 30 GPH flow rate

What Is The Best Small Aquarium Filter For Nano Fish?

Depending on your tank’s size an internal or hang on back filter can work well. Just make sure you use a pre-filter or filter sponge to stop tiny fish being sucked into your filter.

What Is The Best Small Aquarium Filter For Betta Fish?

Various types including internal, HOB and even undergravel filters can be a good choice for your betta fish. The important thing is to ensure they are adjustable so you can reduce the flow rate.

How Often Should I Clean My Filter?

Check your filter weekly and remove any obvious debris to stop it getting clogged. It’s important to only rinse with tank water, never tap water, and replace filter pads around every 3 to 4 weeks.

Photo of author
Matt Thomas
Matt has been keeping fish since junior high when he used to look after his parent's tank. He loves guppies, cichlids, and his crowntail betta named Bobby.

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