Best filters for aquariums up to 20 gallons, many types for choice

Updated: February 9, 2023 - By: - Categories: Equipment

All 20-gallon aquariums need a good quality filter to keep water quality high, and your fish and other livestock healthy. In aquariums without filters, ammonia and nitrites can quickly build up to dangerous levels, while solid waste and debris foul the water. In this article, we introduce many excellent filters for 20-gallon aquariums to help you select the right filter for your needs.

Best 20-gallon aquarium filters

Model Our rating Type Flow rate Ideal for Media
Aqua Clear 30 power fish tank filter editor's ratingAqua Clear 30 power fish tank filter #ad Hang-On-Back 150 GPH, adjustable 10-30 gallons Foam, Activated Carbon, and BioMax
Marina S20 Power Filter editor's ratingMarina S20 Power Filter #ad HOB 92 GPH, adjustable up to 20 gallons filter cartridges with included carbon & zeolite
Aqueon QuietFlow LED PRO 20 power filter editor's ratingAqueon QuietFlow LED PRO 20 power filter #ad Hang-On-Back 125 GPH, adjustable 20-30 gallons carbon cartridge, biological grid
Fluval 107 Performance Canister Filter 120Vac editor's ratingFluval 107 Performance Canister Filter 120Vac #ad canister filter 95 Gal/h (360 L/h) 10-30 Gal (40-130 L) bio-foams, activated carbon
Fluval C2 Power Filter editor's ratingFluval C2 Power Filter #ad HOB 119 GPH (450 L/h) up to 30 gallons (115 L) floss pad, foam, activated carbon, C-nodes, and drip tray pad
Fluval U2 Underwater Filter editor's ratingFluval U2 Underwater Filter #ad internal filter 105 GPH, adjustable 12-30 Gal 2 foam pads, 2 poly/carbon cartridges, and 40 grams BioMax
Hygger Double Sponge aquarium filter editor's ratingHygger Double Sponge aquarium filter #ad sponge filter air pump powered (buy separately) 10-40 Gal 2 spare sponges, 1 bag of ceramic balls
Marineland Penguin PRO Power Filter editor's ratingMarineland Penguin PRO Power Filter #ad Hang-On-Back 125 GPH, adjustable up to 20 Gal Marine Land rite-size B filter cartridge
Penn Plax Cascade 500 Canister Filter editor's ratingPenn Plax Cascade 500 Canister Filter #ad canister filter 115 GPH up to 30 Gal floss pad, coarse sponge
Tetra Whisper EX30 Silent Multi-Stage Power Filter editor's ratingTetra Whisper EX30 Silent Power Filter #ad Hang-On-Back 160 GPH 20-30 Gal Whisper EX carbon cartridge
SunSun Tech'n'Toy HW-602B 106 GPH 3-Stage External Canister Filter editor's ratingSunSun Tech'n'Toy HW-602B Canister Filter #ad canister filter 106 GPH (400L/h), adjustable up to 20 Gal filter pads

20-gallon tank filters reviewed

Aqua Clear 30 power fish tank filter

The Aquaclear 30 power fish tank filter is brilliantly designed to combine user-friendliness while maintaining excellent water quality in your home aquarium. To achieve crystal clear, safe water, this filter uses 3 different filter media to provide biological, chemicals, and mechanical filtration.

Aquaclear 30 installationAquaclear 30 installation #ad

This hang-on-back filter design is easy to install and filters up to 150 gallons of water per hour, although the control is in your hands because the flow rate is fully adjustable if you prefer a lower current strength in your aquarium. While running, this filter disturbs the surface water in your tank, allowing oxygen molecules to enter the water where they become more easily available to your fish.

AquaClear 30 multistage filtrationAquaClear 30 multistage filtration #ad

This filter has an easy-to-follow maintenance schedule for the replacement of its filter media. The Aquaclear Bio Max filter media is designed to provide long-lasting biological filtration by providing a system of fine pores in ceramic rings which create an excellent environment for beneficial bacteria to colonize.

The foam insert provides even more surface area for the establishment of these vital bacteria, while simultaneously performing its primary function of mechanical filtration of particles. Finally, chemical filtration has not been forgotten in the design of this aquarium filter and is provided by the research-grade activated carbon inserts.

Marina S20 Power Filter

For those aquarists with little free space around their aquariums, the Marina S20 Power Filter offers a sleek and compact design that doesn’t fail to deliver on filtration. One of the features of this hang-on-back filter that help to save space around the outside of your tank is the submerged motor on the inlet, which also lowers noise levels.

Marina S20 Power Filter side viewMarina S20 Power Filter side view #ad

The Marina S20 comes supplied with two bio-clear and two bio-carb filters. Both of these are very easy to replace during maintenance operations, saving you time and effort. Chemical, mechanical and biological filtration are all provided.

Marina S20 Power Filter boxMarina S20 Power Filter box #ad

The submerged motor of this filter not only lowers operating noise but also means the unit is self-priming, so you don’t need to fill the filter with water before restarting it after a power failure. An added safety feature is the prefilter sponge which keeps your livestock safe from being sucked into the filter. All in all, this is a great filter for your 20-gallon aquarium.

Aqueon QuietFlow LED PRO 20 power filter

The Aqueon Quiet Flow filter is designed for aquariums of up to 30 gallons, meaning it provides more than enough filtration for a well-stocked 20-gallon aquarium. In addition to the biological, chemical, and mechanical filtration provided, this filter ensures further fine-scale filtration using a specialty filter pad.

This filter features an innovative LED light system that alerts you when the water flow levels are reduced due to a clogged filter, thus indicating when a replacement is due. The unit has a user-friendly internal pump which is both very quiet, and self-priming after a power interruption.

Fluval 107 Performance Canister Filter 120Vac

Fluval’s latest generation of high-performance canister filters is as reliable and powerful as ever, but now 25% quieter and more energy efficient. Amazingly, this unit uses about the same amount of power as a 10-watt lightbulb, saving you money on electricity running costs in the long run.

Fluval performance canister filter energy efficiencyFluval performance canister filter energy efficiency #ad

These filters are designed and built in Europe for 10-30 gallon aquariums. A high-quality, strengthened priming pump makes starting the unit easier than ever. The dual media baskets can be removed and cleaned or refilled without needing to drain the canister, saving you time and creating less mess in your home.

Fluval 107 canister filter maintenanceFluval 107 canister filter maintenance #ad

The Fluval 107 Performance Canister Filter has a 1.45m maximum water column and can be installed well out of sight using the 9.8ft long ribbed hose that is provided. In all, 5 different filter media are included with the filter such as 3 varieties of bio-foam, activated carbon, and quick clear. This is a trusted canister filter for correctly stocked 20-gallon aquariums.

Fluval C2 Power Filter

This Hang-on-back filter for fresh and saltwater aquariums provides an impressive 5 stage filtration process. This includes 2 stages of mechanical filtration using both polyester and foam filtration media. Activated carbon ensures effective chemical filtration, and dual-phase biological filtration is made possible using both Bioscreen and ceramic nodes which house beneficial bacteria.

To further enhance the efficiency of filtration, water is recirculated multiple times within the filter for incredible results. This filter has an adjustable flow and a telescopic intake pipe giving you greater control of the water flow in your aquarium. An additional feature is the innovative pop-up tab that indicates when filters are due for replacement.

Fluval U2 Underwater Filter

This underwater filter has a sleek design and is suitable for use in both fresh and saltwater aquariums. The filter can be positioned both vertically and horizontally, the choice is yours. The filter cartridge is easily accessible using the well-designed flip-top lid, making replacement and maintenance quick and easy.

The 3 stage filtration process is provided using foam, poly/carbon cartridge traps, and finally Biomax, which provides optimal biological filtration. Furthermore, with 3 outputs, you can adjust how the water flows from the filter into your aquarium.

Hygger Double Sponge aquarium filter

This air-powered filter creates a gentle water flow, oxygenates the water, and provides excellent mechanical and biological filtration. The filter is easily secured inside the tank using the 2 supplied suction cups. In order to operate this aquarium filter, you will need an air pump and a length of airline tubing, both of which are sold separately. The large sponges of this filter trap waste particles and provide a perfect environment for colonies of beneficial bacteria.

Bio-ceramic media balls are included with this filter and act as another effective media for biological filtration. You are, however, free to use additional filter media of your choice in the compartments, allowing you to customize the filtration in your aquarium.

Marineland Penguin PRO Power Filter

The Marineland Penguin PRO is a sleek and stylish hang-on-back style power filter for aquariums of up to 20 gallons. This unit uses the Marineland rite-size B filter cartridge to provide great biological, chemical and mechanical filtration. Furthermore, an extra slot is provided should you wish to use a second rite-size B cartridge for additional filtration and even better water quality.

In addition to the filtration provided by the cartridge, this unit benefits from the wet/dry biological filtration provided by its bio-wheel technology. This filter has an adjustable flow and a submerged motor with a dampener for reduced running sound levels.

Penn Plax Cascade 500 Canister Filter

The Penn Plax Cascade 500 canister filter can be used for both fresh and saltwater aquariums. The filter has two large-capacity media baskets which you can fill with a combination of filter media of your choice, although floss pads and coarse sponge is included with your purchase.

The filter is easily primed at the push of a button and has adjustable 360-degree rotating valve taps, where flow valves can be removed from the filter for easy maintenance without removing hoses and fittings from the aquarium itself. This canister filter comes with a spray bar which effectively spreads out the outflow from the filter while oxygenating the water in your aquarium.

Tetra Whisper EX30 Silent Multi-Stage Power Filter

As the name implies, this hang-on-back filter from tetra is whisper-quiet. No priming is required and this filter is very easy to set up and maintain. Filter cartridges are easy to replace, saving you time and mess.

Four-stage filtration is provided using coarse floss for mechanical filtration of large waste particles, carbon filtration, which removes odors and impurities, multi-density floss for the removal of fine particles, and bio-scrubber which creates biological filtration to remove ammonia and nitrites.

SunSun Tech’n’Toy HW-602B Canister Filter

This small canister is easy to open and has a small motor that runs extremely quietly and is easy to remove from the side of the canister for maintenance. This canister filter can be used for aquariums of up to 20 gallons but, with a flow rate of 106gph, it is ideal for well-stocked tanks of around 15 gallons. The intake pipe can be lengthened using an extension to suit taller tanks.

With this filter, you have the option of using the adjustable spout or the spray bar which distributes the water outflow so that the current created is not overly strong while oxygenating the water to keep your livestock healthy. This affordable filter includes 4 different sponge pads, providing great mechanical and biological filtration in cycled aquariums, although you have the option of using a filtration media of your choice.

Frequently asked questions

Do I need a filter for my 20-gallon aquarium?

You should never keep fish or other aquatic animals in a 20-gallon aquarium that has not been fully cycled and fitted with an effective filter. Not only does the filter keep the water looking and smelling great, but it also keeps the water safe and healthy for your fish and other animals.

Are filters dangerous for my fish?

Filters are very important for the health of your fish. They are not dangerous unless you use a filter that creates a very strong current in your aquarium that may cause stress on your fish. Filters with large inlets should also be covered with a pre-filter to prevent the possibility of small creatures being sucked into the filter or becoming trapped against the inlet.

How do I choose a flow rate for my 20-gallon aquarium?

To calculate an appropriate flow rate for your aquarium, simply multiply the gallons of your tank by between 4 and 6. This gives you an ideal flow rate of between 80 and 120 gallons. This is more of a guideline than anything else and it does vary depending on what kind of tank you have and the kinds of fish that live in it.

Generally, heavily planted tanks do better with lower flower rates, especially where CO2 is used to promote better and faster plant growth. On the other hand, some kinds of fish like danios and hillstream loaches enjoy stronger currents and a higher flow rate. Be sure to provide some hardscape structure in aquariums with higher flow rates to create calm areas where slower swimming fish like puffers can escape the current and rest when necessary.

Final Thoughts

With so many different makes and models of aquarium filters available on the market, deciding on just one can be a pretty difficult decision. The selected filters on this page are all ideal choices, so you don’t need to stress about whether they will suit your needs. Choosing a filter for your 20-gallon aquarium from this list is a great start towards keeping a healthier and more beautiful fish tank.

We enjoy keeping fish, and have for many years. We are trying to promote the hobby as much as possible. We want to see many others succeed in their fish keeping efforts and are committed to sharing our knowledge when we can.

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