Best Filter For 20 Gallon Tank – The Ultimate Buying Guide

Best Filter For 20 Gallon Tank

Aquariums are closed-off ecosystems that must be sustained through the efforts of the aquarist. Filtering is one way this can happen, and it’s critical to choose a filter appropriate for your needs.

If you have a 20-gallon aquarium, then the best filter for your tank depends on what kind of fish and plants you want to keep. 

There are many different types of filters available for 20-gallon aquariums, but which filter is best? 

This blog post will go over the top 10 best filters for your tank and help you decide what to buy. 

What Type Of Filter To Choose For A 20 Gallon Aquarium?

Take a look at the following if you’re pondering which type of filter to use in your 20-gallon fish tank. I’ll break down each option with pros and cons so that you can make an informed decision about what’s suitable for your personal needs, then share 10 of my favorites!

Hang On Back (HOB) Filters

The primary type I recommend for a 20-gallon tank is Hang-On-Back (HOB) filters, also known as power filters.

The HOB filter is a simple, compact piece of equipment. The filtration used by this type is straightforward – the water goes into a lift tube, and it enters an enclosed chamber where it’s going to be cleaned up with filter media inside there. So, these guys push water through filter media to clean before pumping back in!

HOB filters use a combination of mechanical, biological, and chemical filtration to remove harmful particles from your fish tank. 

The foam filter removes particulates while bacteria colonize on the ceramic ring for better biological filtering.

They’re equipped with activated carbons or resins inside their chambers for chemical filtering purposes too!

Related post: 06 Best Aquarium Bio Media (Make Your Aquarium Biologically Balanced)

Power or HOB filter in a nutshell


  • Cost-effective filtration
  • Compact
  • Standalone filter for 10-50 gallons


  • Frequent cleaning or replacing once 3-4 weeks 
  • Noisy

Internal And Submersible Filters

Internal and submersible filters have the ability to be submerged underwater, powered by an electric pump or air pump. 

Near the suction line of these pumps is where you will find a casing that holds filter media, such as sponges that work mechanically to trap waste materials in their porous fine mesh material body.

In addition to mechanical filtration, internal filters also provide a place for bacteria colonies to grow. Some models even have an additional layer of chemical filter media.

Internal Filter in a nutshell


  • Space saver
  • Operate by both air pump and electric pump


  • Tricky maintenance

Canister Filters

Canister filters are high-tech, the best choice for large tanks, but many smaller models also work well in a 20-gallon tank.

They offer superior filtration to any other filter; however, they will cost you more upfront but require less maintenance. So, it’s your decision to select the priority – the cost versus comfort!

Canister filters are equipped with a high-powered pump. The pump sucks the water from the tank through an inlet tube, passing it through filtering media placed inside a canister that removes impurities and polishes crystal clear water back into your fish’s habitat.

Canister Filter in a nutshell


  • Superior and better filtration 
  • Less maintenance 
  • Low noise
  • Adjustable flow
  • Customizable filter media options


  • Frequent cleaning or replacing once 3-4 Expensive
  • Requirement of careful maintenance

Undergravel Filters

Undergravel filters consist of plates with small holes buried into gravel bedding materials under aquariums while keeping their top lifted out above this material surface level.

So, they sit beneath a layer of gravel or other substrate and work to trap debris as water flows through it. The clean, filtered water then rises up from inside the elbow, where activated carbon is placed for chemical filtration before being distributed back into the aquarium again!

The large surface area of the undergravel filters ensures adequate biological filtration, and since water is continuously circulating through substrates, all layers get oxygenated. This helps build aerobic bacteria that convert all waste into usable nutrients in a planted tank.

The massive benefit to an aquascape with these filters is that they provide continuous aeration inside your substrate, which builds up beneficial aerobic bacteria and converts any wastes back into nutrient-rich material for plants!

Related post: How to Increase Oxygen in Fish tank? (11 Proven Ways to Follow)

Undergravel filter in a nutshell


  • Very inexpensive 
  • Better biological filtration than any other type
  • Simple mechanism 
  • Long-lasting


  • Constrained mechanical filtration
  • Limited substrates option

Sponge Filters

Sponge filters are the simplest type of aquarium filter. They use sponges as their filtration media, remain fully submerged in water, and are most often powered by an air pump to suck dirty water through it. 

The outlet for this system is connected inside a housing with a tube that sucks up dirty, stagnant waters from your fish tank just like lungs inhale oxygen into our bodies!

The sponges in your fish tank provide mechanical and biological filtration. 

The large surface area of the sponge increases its ability to attract beneficial bacteria. 

Sponges are often used with other media like charcoal or zeolite for chemical filtration purposes.

Sponge filter in a nutshell


  • Simple design
  • No moving parts
  • Low operating cost
  • Gentle water flow
  • Inexpensive


  • Relatively weak mechanical filtration
  • Require frequent water changes

Choosing Filter For 20 Gallon Aquarium

The flow rate of your filter can be a great way to determine the size you need.

When selecting a filter size, the water in your tank should pass through it four times per hour. So, for example, for a 20-gallon aquarium, you would want an 80 GPH flow rate or more; never undersize!

Oversizing your unit is always better than under sizing because if anything goes wrong with the water filtration system, there are no worries about running out so quickly!

At the same time, you should not expose your fish to too much flow, but some aquarium filters have built-in flow control mechanisms that can help you.

10 Best Filter For 20 Gallon Tank Reviewed

The AquaClear Hagen Power Filter is a 3-stage aquarium filtration system that offers superior contact time with filter media and energy efficient pump that lowers operating costs.

It provides optimal mechanical, chemical, and biological filtrations. Quick and easy installation makes this Hagen aquarium filter perfect for any setting.

This HOB filter is a quiet, efficient operating power filter that I highly recommend for any 20-gallon aquarium owner. In addition, the filtration media provided with the Aqua Clear comes complete with an AquaClear foam insert and activated carbon; this makes it perfect for anyone looking to keep their clean water crystal clear!

I love this HOB filter. It has a bottom-up design that ensures all your aquarium water goes through the filter bed, and it comes with features like large filters containers to customize for different users’ needs.


  • Quiet
  • Durable
  • Customization of filtration media
  • Adjustable flowrate
  • Easy installation


  • Expensive media bags

GRECH CBG-800 Hang-On Back Filter is a high-quality hang-on-back filter that offers an adjustable 211gph flow rate with a surface skimmer to eliminate undesired surface films. In addition, this aquarium filter features a 5W UV Sterilizer, which helps eliminate algae and bacteria, keeping your aquarium water crystal clear.

So, this external HOB filter is great if you need to eliminate bacteria and algae. The UV sterilizer kills all of those pesky microbes, while the carbon media will remove foul odors from your tank water.

Plus, it has the most vital bio-media that helps keep the fish healthy by removing any chemicals or toxins they may accumulate in their home!

The UV sterilizer is simple to operate – just switch it on/off when necessary. What’s more? The filter is very efficient at cleaning the tank of stubborn green slime and keeping a clear water environment for your fishy friends.


  • UV sterilizer
  • Adjustable flow 
  • Easy to install
  • Silent operation
  • Surface skimmer


  • Tight media basket
  • Low-quality carbon media

Aqueon QuietFlow LED PRO aquarium power filter is ideal for up to 20-gallon aquariums. It features a self-priming pump that auto-starts initially or restarts if power is interrupted and restored. In addition, it provides mechanical, chemical, biological, and optional specialty pad filtration.

The self-priming system ensures that you do not have to prime your filters by hand, which can be time-consuming with so many other tasks on one’s mind!

With four stages of filtration, these systems will work hard removing all dangerous encounters from aquarium water – leaving only pure goodness in its wake.

This aquarium filter features a quiet pump design with high flow rates to help keep your fish happy and healthy.

The Aqueon QuietFlow LED PRO Aquarium Power Filter also includes an easy-to-use cartridge change indicator, so you know when it’s time to replace the filter media.


  • Self-priming feature
  • Four-stage filtration
  • Quiet operation
  • Lifetime warranty
  • Cartridge change indicator


  • Bulky unit

Marineland Penguin Power Filters are the perfect choice for your aquarium. The Marineland Penguin Power Filter is a 3-stage filter that mechanically, chemically, and biologically filters your water through a pad of double-thick poly fiber. It also uses Rite-Size packaging to make it easy to choose the right size replacement cartridge for your filter.

Marineland’s Filters are designed for people who want a clean tank environment without the hassle of complicated assembly work. They have an innovative design that includes replaceable 3 pack filter cartridges that fit Marineland’s PRO filters 100, 125, and 175, as well as their original power filter 150, so it is easy to install pre-assembled cartridges.

The Marineland Penguin Power Filter features BIO-Wheel technology which provides wet/dry filtration while keeping your aquarium sparkling clean. In addition, this power filter comes with a ribbed backing that ensures the even distribution of carbon for sparkling clean water.


  • Easy to operate
  • Reliable
  • Color-coded packing
  • Quiet
  • Easily replaceable cartridge


  • Not self-priming
  • Costly replacement cartridges

NICREW Aquarium Internal Filter is the most energy-efficient and reliable filter for your aquarium. It has a compact size that makes it easy to install, plus its durable materials make sure you can use this product long-term without expensive maintenance costs.

The NICREW Aquarium Internal Filter generates abundant air bubbles and water flow, which are optimal for oxygen supplement and water circulation of the aquarium.

The adjustable air regulator distributes a gentle water flow, making it safe even if you have delicate fish or shrimp in your tank!

NICREW Aquarium Internal Filter is an excellent combination of biological and chemical filtration.

It provides effective and thorough biological and chemical filtration, creating a superior aquarium water environment. Activated carbon and fine filter foam trap debris and fish waste, absorb odors.


  • Silent
  • Easy-to-install
  • Cheap
  • Spray bar 


  • No easy flow adjustment 

This internal filter from Fluval is rated for up to 30-gallon tanks. It installs easily, offers mechanical, chemical, and biological filtration – making it an ideal choice for your aquarium!

This unit can be horizontally mounted if you have a smaller tank or maintain a low water level. But you can place it vertically against your aquarium wall to create currents and customized flow patterns.

Putting your hands on the glass, you can feel vibrations that shake from below. They are caused by a silent impeller drawing water in and pushing it outwards towards an even flowrate, and only silent bubbles can be heard.

For deep agitation in your tank, try setting it to Bottom Output but for gentle flow, choose Spray Bar. If you’re looking for maximum circulation with oxygenation, then put it to Top Output.

The convenient flip-top lid allows for quick and easy access to the filter cartridge.


  • Multi-stage filtration
  • 3-way flow control
  • Vertical & horizontal placement
  • Easy filter replacement
  • Suitable for freshwater and saltwater


  • Small media basket

The Clear-Free Premium Under Gravel Filter is a unique system that combines an under gravel filter with an air-driven aeration system. The two systems work together to create the ideal environment for your fish and plants in aquariums up to 20-gallon.

This innovative design provides you with the convenience of not having to deal with messy tubes, hoses, or cords!

Air is delivered through small holes in the top of the unit and down into the gravel bed, where it bubbles back up into the water column providing oxygenation for your fish.

The Penn Plax Clear-Free Premium includes an activated carbon cartridge that removes odors and discoloration from the water. It also consists of a pre-filter sponge, air stones, lift tubes, intake tubes, and suction cups to help you get started right away.

When enough time is allowed for water to pass through, anaerobic bacteria collect on the filter plates and gravel.


  • Adjustable lift
  • Easy to install & clean
  • Inexpensive
  • Durable


  • No mechanical filtration

Lefunpets Sponge Filter is a new generation of aquarium filters. It is made from high-quality materials, which can be used for a longer time than other filters.

It uses natural air to power the water flow and sponge material to filter out debris and waste particles from your tank to keep your fish healthy and happy.

The Lefunpets Sponge Filter has a unique cylindrical shape 6 vertical stripe sponge design, making it possible to trap floating debris without sucking up your fish.

The filter also provides an area for beneficial bacteria to grow, increasing the biological filtration of aquariums with its porous material that has a surface area up to 10 times greater than similar filters!

When it comes to cleaning your fish tank, this sponge filter is a great choice. You can easily detach all of its parts for easy and thorough clean-up. Then, all you have to do is just squeeze them in the water!


  • Inexpensive
  • Non-complex design
  • Gentle water flow 
  • Easy to clean


  • Requires frequent cleaning 

Fluval 106 External Filter is a multi-stage filtration system that provides healthy fresh and saltwater aquariums. It is designed for aquariums up to 25 gallons.

Fluval 106 External Aquarium Filter offers effective filtration, which is ensured by the twin foam pre-filters that clear your water from debris and prevent frequent clogging.

The filter also includes two other chemical and biological filters for a total of five stages of filtering media so you can be sure to remove all impurities from your fish tank’s water.

It features an Aquastop Valve that prevents water from flowing back into the tank and ensures water flow without leaks.

The filter has a patented impeller design that makes it run quieter than other filters on the market.


  • Easy maintenance
  • Beginners-friendly
  • Multi-stage filtration
  • Aquastop valves 
  • Self-priming


  • Too powerful flow

Penn Plax’s Cascade Series Aquarium Filters are perfect for freshwater or saltwater tanks and offer high-quality features with a user-friendly design.

This Penn Plax Cascade 500 Canister Filter is perfect for aquariums up to 30 gallons.

It has two media baskets that allow you to customize your filtration needs and a spray bar that will help oxygenate the water in your aquarium.
With its push-button primer, this canister filter is easy to prime and maintain.
This product also comes with a 1-year manufacturer’s warranty!

You don’t have to worry about your canister filter being too loud with this one. It is so quiet that you would never know it was there if not for the peace of mind knowing all is well in the tank.

The flow valves are also easily maneuverable, making setup and maintenance a breeze!


  • Very silent
  • Easy to install
  • Suitable for both freshwater and saltwater 
  • Adjustable flow rate
  • Easy push-button primer


  • High power consumption

Final Words

I hope you found this article helpful in your search for the Best Filter For 20 Gallon Tank. The 10 best filters listed above should make picking one that fits your needs and wishes easier.

All you need to do is consider your specific needs and wishes before making any purchase decision and choosing the best product for your circumstance!

If there is anything else you want to know, please leave a comment below!

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