Best Filters for 20 Gallon Aquarium Fish Tank

Getting the best filters for 20-gallon aquariums can be tough with so many different types of filters available on the market. With so many options for your fish tank filters including canister, power, and interior filters, we will try to make it easier for you to choose the best filter for your 20 gallon tank.

For any beginners who are not familiar with the various kinds of fish tank filters, you can read through our reviews and guide below. And for any old hand who is experienced with the workings of fish tank filters and searching for the best cleaners for 20-gallon aquariums, the best choice should instantly pop out at you. This detailed review is intended to let you make the most informed decision, so let's not waste any more time and get to the filters.

Fluval 107 Perfomance Canister Filter	Fluval C2 Power Filter	Aqua Clear Fish Tank Filter 5 to 20 Gallons 110v
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Powerful canister filter, superior filtration, options for inline heater and you can hide it under you stand!	Hang on back design, 5 stage filtration, filter cartridges.	Simple design, hang on back, filter cartridges.
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Fluval 107 (external canister filter) 20-25 gallon aquariums

This filter is a suitable choice for hobbyist who prefers filtering their aquariums with this type of filters. This type of filter is costlier than the internal or power filters.

The filter container is much bigger compared to other tanks of the same capacities. It features two big filter media containers that can accommodate various filter media. The large-sized filter allows it to contain more filter elements which help in efficient filtration.

The canister filter can rate for tanks as large as 25 gallons, which makes it a perfect choice if you are looking for the best filters for 20-gallon aquariums.

Pros:
Superior 3-stage filtration performance
Large size filter
Powerful and flexible flow rate,
Impeller for noiseless operation,
Ready-to-use priming by pushing the button on the lid,
Low maintenance
Can find replacements,
Three-year warranty.

Cons:
Need space under your fish tank stand.

Fluval C2 (power filter) 20-25 gallon tanks

Fluval C2 power filter is a first-rate power filter produced by the renowned brand, Hagen Fluval. It features almost all you require to start. It comes with activated carbon that provides efficient chemical filtration, C-nodes for increasing growth of good bacteria for biological filtration, as well as foam padding for mechanical filtration.

The unique quality of the power filter is the five-stage filtration which keeps the water in your fish tank clean and provides a fresh atmosphere for your aquatic fish to survive.

The Filter Includes:
Stage One and Two: Foam padding that mechanically eliminates wastes in the water.
Stage Three: Activated carbon extracts minerals, strong smells and discolorations keeping the water super clean
Stage Four: Bio-Screen provides biological filtration mode.
Stage Five: C-Nodes offer an optimal living area for reliable nitrifying bacteria that process nitrogen pollutants in the water.

Pros:
Five-stage filtration,
Maintains the water
Adjustable flow rate,
Easy to use filter media,
Easy installation and maintenance
Quiet operation.

Cons:
Smaller filtration capacity compared to other similar 20 gallon filters

AquaClear 20 (power filter) 20 gallon aquarium

The AquaClear 20 is a power filter and is our top choice of the best filters for 20-gallon aquariums. It comes with a higher media capacity as opposed to other similar aquarium filters that have the same tank volumes. The high filtration capacity makes the filter flexible and effortless to maintain the filter media. This feature makes the AquaClear 20 power filter popular and highly-rated on the marketplace. Besides, you can also select other filter elements to operate the filter even without using the materials from the industry.

The Aqua Clear 20 also features filter elements such as the AquaClear foam, BioMax, and activated carbon. These materials are essential for use in installing an entire system with biological, chemical, and mechanical filtration. Equipped with the framework of all filtration system, the filter guarantees that the water passing through the filter is suitably clean and pure for the aquatic plants and fish to thrive in the aquarium.

The power filter comes with 100 GPH (gallons per hour) flow rate, which makes it sturdy enough to hold an aquarium with a capacity of 20 gallons for an extended time. It has a flexible flow rate, which can fit in different tank capacities and types of fish.

You can reduce the rate of the flow to about 50% without interrupting the efficient filtration system as it has a secured re-filtration method. The Aqua Clear 20 power filter is an ideal choice for the hobbyists who are looking to create a filtration system on their own.

Pros:
It keeps and filters the water pure and clean
Big sized tank to hold high filter media
Flexible and easy to use filter materials
Adjustable flow rate
Low-maintenance cost
Quiet operation
Two-year warranty

Cons:
Uses cartridges that require more frequent cleaning

Marina Slim S20 (Power Filter) 20 gallon fish tank

This is another high-rated power filter for 20 gallons aquariums and is suitable for both the beginners and old hands. It comes with a closed-back design for easy installation and can fit even in little spaces.

The power filter also features the flexible flow control making it a perfect choice for the smaller capacity of 20 gallons. This power filter operates at a lower noise level without disrupting its filtration performance. It automatically starts on installation and begins filtering even without manual operation.


The only downside of the Marina Slim S20 power filter is it has lesser filter capacity, and you will also need to purchase the cartridges to maintain it. Nevertheless, the filter material for biological filtration featured in the cartridges prevents harmful nitrogenous pollutant from degrading the aquatic lives in your aquarium.

Pros:
Small design
The high-quality filter keeps the water pure and clean
Efficient biological filtration
Adjustable flow rate
Easy to install and maintain
Quiet operation

Cons:
Limited filter volume compared with AquaClear power filter
Need to use the manufacturer’s cartridges
High maintenance cost for purchasing cartridges.

Whisper (internal filter) 20 gallon fish tanks

The Whisper is an internal power filter that fits and runs in the interiors of the aquarium. Easy to mount and use, it is ideal for beginners. It includes the Bio-scrubber pad which provides excellent biological filtration and offers a 3-stage filtration system.

The pad enables helpful bacteria to flourish in the aquarium. The Whisper biological-bag cartridge features an activated carbon that discharges waste particles, discolorations, odors, in the tank water.

Pros:
It features the Dirt cheap
The Bio-scrubber provides exceptional biological filtration
Lower noise level
Suitable for low-intensity water and turtle tanks

Cons:
It can take ample space in the tank
Fewer media capacity compared to canister and power filters
Cannot adjust flow rate,
Need to apply or use the manufacturer's cartridge

Penn Plax Cascade 500 (canister filter)

This is a tiny and small canister filter for tanks as big as 25 gallons capacity. It comes with a versatile filtration container to hold any filter materials you need. It also features filter media including bio-floss, activated carbon, bio-sponges, to offer all 3-stage filtration that thoroughly filters your fishbowl water.

Pros:
It is affordable
Large volume for an exceptional performance of the three-filtration system
Powerful and flexible flow rate,
Ready and easy priming by pressing the switch on its top,
Valves for controlling flow rate and easy to lift clamps for easy installation and maintenance.

Cons:
Less durable compared with Fluval 07 model canister filters.