external power (Hang On Back) filter

There are many filter types which you can choose for a 20 gallon fish tank, they include power, canister, and internal filters. They are the most popular and powerful filters today. In this review, I will cover some of the best 20 gallon aquarium filters which come in various types for you to choose.

If you are a beginner and don’t know about any filters, you should acquire some knowledge about some popular types of aquarium filters to easily understand the filters in this review.

Best power filters for 20 gallon aquariums

Power filter, also known as Hang-On-Back or HOB filter, is a powerful filter designed to work outside the aquarium. Power filters often provide all three types of filtration (mechanical, biological, and chemical) that really make your aquarium water clean and clear, and provide a healthy environment to make your fish thrive. Following are some high-quality power filters rated for 20-gal tanks.

AquaClear 20 power filter

  • aquaclear-20-power-filter-for-20-gallon-aquariumEditor's rating: Check on Amazon.com
  • Type: power filter
  • Flow rate (gallon per hour): 100 GPH, adjustable
  • For tank sizes: 5 to 20 US gallons
  • Filtration types: All 3 types of filtration
  • Product includes: AquaClear Foam, Activated Carbon, BioMax and Cycle Guard.
  • Filter sizes: 4.5 x 7 x 6.5 inches

AquaClear 20 Power Filter is the very popular and powerful power filter in the market and its quality is proven by thousands of aquarists on the world. The filter has a larger capacity compared to other comparable filters that gives it the most filtration efficiency to keep your aquarium water clean and clear.

The filter comes with some filter materials like AquaClear Foam, Activated Carbon, BioMax and Cycle Guard that are necessary for the most effective filtration system. With a grid includes all types of filtration in mechanical, biological, and chemical, you know that all the water in the tank goes through the filter and is safe for your fish.

What make it the most favorite filter of many hobbyists is its customization in using filter media with the large capacity. You can use your own filter materials to work with the filter but not have to use ones that are same to the product. People love to use the filter with only 2 filtration types (biological and mechanical) to provide the ultra-clean environment for their fish; and they only add Activated Carbon media to perform the chemical filtration when the aquarium water looks yellowish.

The filter features a flow rate of 100 gallons per hour which is strong enough to keep tank with 20 gallons of water clean and clear for a long period. The flow rate can be adjustable to fit various tank sizes and fish types, so don’t worry if it is too strong for your tank. With its very affordable price, quality, and customization, I strongly recommend this for the creative aquarists who want to build their own filtration system. It is surely the best power filter as well as the best 20-gallon aquarium filter for my choice.

Fluval C2 power filter for 20-25 gallon tanks

  • fluval-c2-power-filter-for-20-gallon-aquariumEditor's rating: Check on Amazon.com
  • Type: power filter
  • Flow rate (gallon per hour): 119 GPH
  • For tank sizes: 10-30 US gallons
  • Filtration types: All 3 types of filtration
  • Product includes: Fluval C2 Poly/Foam, Activated Carbon, C-nodes and drip tray pad.
  • Filter sizes: 4.5 x 6 x 8 inches.

This power filter is very similar to the previous. It is also manufactured by Hagen Fluval, a well-known brand by their high-quality aquarium products. The filter includes everything you need to get starting: the activated Carbon for chemical filtration, the C-nodes is needed to have colonies of helpful bacteria for the most biological filtration (remove nitrite and ammonia), and the foam blocks to mechanically filter the waste.

Marina Slim S20 Power Filter

  • marina-s20-power-filterEditor's rating: Check on Amazon.com
  • Type: power filter
  • Flow rate (gallon per hour): 92 GPH
  • For tank sizes: up to 20 US gallons
  • Filtration types: All 3 types of filtration
  • Product includes: 4 filter cartridges: 2 Bio-Carb (contains activated carbon and Ceramide) and 2 Bio-Clear (contains zeolite and Ceramide).
  • Filter sizes: 3.8 x 11.5 x 6.4 inches.

I like Marina because of their quality aquarium kits like the Marina LED aquarium kits for starters. Most of their products are absolutely quality and they have satisfied many customers from the new comers to advanced hobbyists. You can easily notice that when you read the reviews of Marina’s products.

The only drawback of this filter is its capacity smaller than the Aquaclear 20 and you have to buy the filter cartridges for the maintenance. However, the abundance of biological filter materials (zeolite and Ceramide) included in the filter cartridges ensure that harmful nitrogenous toxins (ammonia and nitrite) are degraded and no longer harm your aquarium inhabitants. So, it is worth for your money.

Whisper® internal filter for 20 gallon tanks

  • internal-filter-for-20-gallon-aquariumEditor's rating: Check on Amazon.com
  • Type: internal filter
  • Flow rate (gallon per hour): 125 GPH
  • For tank sizes: 10-20 gallons
  • Product includes: one pre-assembled Whisper Bio-Bag filter cartridge.
  • Filter sizes: 4.9 x 5.4 x 10.2 inches.

This is an internal filter (or internal power filter) which is placed and works inside your aquarium. It is the most traditional filter type that are very familiar with most hobbyists, even the new comers. The filter is compact, cheap, easy to install and use. Only assembling the filter and position it inside your aquarium and it will do the work to keep the tank clean and clear. If you love to use internal filter, this one is designed for you.

Best canister filters for 20-25 gallon aquariums

The design of a canister filter is that its filter chamber is larger than other filter types and is divided into different baskets for accommodating various types of filter media. Because its capacity is much bigger than other filter types, it has the advantage of containing more filter material for the maximum filtration and longer periods between maintenance times.


Most aquarists prefer to filter their tanks with a canister filter despite the fact that they are usually much more expensive than other filter types rated for the same tank size. They are common designed to use on medium to extra large aquariums; however, there are a few ones rated for small tanks.

Fluval 106 external canister filter for tanks up to 25 gallons

  • fluval-106-canister-filter-for-20-gallon-aquariumEditor's rating: Check on Amazon.com
  • Type: canister filter
  • Flow rate (gallon per hour): 145 GPH
  • For tank sizes: up to 25 US gallons
  • Filtration types: 3 types of filtration
  • Product includes: Instant-prime system; single-motion lift-lock clamps; clog-proof intake strainer; dual-layer foam screen; and quick start guide.
  • Filter sizes: 2 x 2.8 x 7.5 inches
  • Used in: both fresh and saltwater aquariums.

Fluval is well-known brand with their canister filter products for many different tank sizes from small 20 gallon to extra large ones used for ponds. These are the most advanced filters used for aquariums in the market today. They feature a very large filter capacity to provide the most biological filtration.

Fluval 106 canister filter is one of the filters in 06 series from Hagen Fluval used for aquariums up to 25 gallons and certainly it is the best canister filter for your 20 gallon aquarium. The Fluval 106 filter is very easy to setup and maintenance; it comes with two filter baskets which are already packed with filter media for quick installation.

Read the full review of Fluval 106 canister filter: https://lovefishtank.com/fluval-106-206-306-406-canister-filter/.

Finnex PX-360 Compact canister filter for tanks up to 25 gallons

  • Finnex PX-360 Compact canister aquarium filterEditor's rating: Check on Amazon.com
  • Type: canister filter
  • Flow rate (gallon per hour): 95 GPH
  • For tank sizes: up to 25 US gallons
  • Filtration types: 3 types of filtration
  • Product includes: durable water intake strainer, spray bar and filter hanger.
  • Filter sizes: 4.8 x 7.2 x 8.1 inches
  • Used in: both fresh and saltwater aquariums.

This is also a small and compact canister filter for medium tank size up to 25 gallons. The filter features multiple removable filtration chambers to contain any media you want. It also come with some filter media such as activated carbon floss pad, sponge, and ceramic rings to perform multi-stage filtration and completely purify your aquarium water.

1 comment

  1. Great filters! Now I have chosen a new one for my 20 gal tank. Tanks, quite nice article.


Leave a Reply

Your email address will not be published. Required fields are marked *