Best Filter for 20-gallon Tank

Whether you intend to buy an aquarium or already have one, you’re probably going to need a filter too. In this article we have compiled a list of the best filters suitable for a 20-gallon fish tank and included a rundown of their key features.

There’s even a handy Buyers Guide to help you make an informed purchase.

Got places to be? Don’t flounder! Here’s a quick link to our top pick and a few reasons why we think you’ll love it.

MarineLand Penguin Bio-Wheel Power Filter

  • Patented Bio-Wheel technology provides excellent wet/dry biological filtration.
  • Delivers mechanical, chemical, and biological aquarium filtration to maintain a clean aquatic environment.
  • Available in 75 GPH, 100 GPH, 150 GPH, 200 GPH and 350 GPH sizes.
  • Product Dimensions : 8.25 x 6 x 7.38 inches; 1.86 Pounds


The first filter on our list is this Penguin Bio-Wheel Filter from MarineLand. This filter is suitable for tanks up to 30 gallons, so it’ll be more than capable of handling a 20-gallon tank.

MarineLand is a reputable brand that’s loved worldwide for its commitment to the quality and performance of its fishkeeping products.

One of its best offerings is this filtration system used to keep tanks clean for a healthy fish environment.

This filter offers three-stage filtration that includes chemical, mechanical, and biological filtration.

It also comes with a cartridge, making it ready to use straight out of the box. Also, this item is made with activated carbon to ensure max efficiency.


  • Can filter up to 30 gallons
  • 3-stage filtration system
  • Patented BIO-Wheel
  • Black Diamond Premium Activated Carbon
  • Technically advanced accessory


  • This filter may require frequent changing


Next up on our list is the Whisper EX Silent Power Filter made by Tetra. Tetra Whisper EX30 Power Filter is an intuitive, easy to use filtration system.

Every feature of the Whisper EX has been designed with simplicity and convenience in mind. The outflow maximizes water agitation and oxygenation and the carbon filters allow for increased efficiency.

This filter is ready to go right out of the box with no priming required. Also, its continuous flushing action prevents debris buildup with scientifically engineered water flow.

This filter is ideal for 20-30 gallon aquariums. 


  • Provides silent multi-stage filtration for clear clean water
  • Sets up easily right out of the box – no priming required
  • Moves water continuously to prevent debris buildup
  • Design minimizes dripping to make cartridge changes easy


  • Some Amazon reviewers found this filter a little noisy


Next is the Quietflow E Internal Power Filter from Aqueon. This is an internal filter, meaning literally that it sits inside the tank.

It will be fully submerged in the aquarium, so no additional space is required for housing. This version works with 30-gallon fish tanks, so your 20-gallon aquarium should be no problem for it.

This filter even lets you adjust the flow rate and direction of the filtered water. Also, you can regulate the height of it.

It’s worth noticing that the filter comes with a 3-stage filtration system for getting rid of debris, toxins, and odors and also removes ammonia and nitrates from the water as a biological filtering stage.

The internal filter cartridges are fully replaceable. This means that the device will have a longer working period compared to other products.

However, you have to buy these parts yourself because they’re not included in the standard package.


  • Provides chemical, biological, and mechanical filtration
  • Auto-start pump requires no priming, automatically restarts if power is interrupted and restored
  • Easy to install using suction cups and/or hanging clips
  • Limited Lifetime Warranty


  • The standard package doesn’t come with replacement filter cartridges


Our next addition to this list is a HOB filter, meaning it hangs on the back of the aquarium. This model from Aqua Clear comes with built-in biological, chemical, and mechanical filtration systems. 

So, you don’t have to set these up separately by yourself. To make the most out of this filter, it is recommended to clean its components every 2 weeks.

This way, you’ll get a much better performance rate. It’s worth mentioning that the product comes with a refiltration system as well which includes an energy-efficient pump to lower maintenance costs.

Also, the installation is easy and quick. No technical knowledge is required to make it work.


  • Quick and easy installation
  • Provides optimal mechanical, chemical, and biological filtrations
  • Comes equipped with AquaClear Foam, Activated Carbon Filter, and BioMax and Cycle
  • Guard for superior water quality
  • Filtration volume is up to 7 times larger than comparable fish tank filters


  • This filter has to be cleaned more regularly than other options on the market


The Penn Plax Aquarium Filter is another great choice for an aquarium filter. It is a hang-on type filtration system that works quietly to deliver up to 100 gallons of water per hour, keeping your aquarium clean for healthy fish.

It can help keep your tank water clear for a healthy living environment for your fish. The Bio-Falls Quad-Filtration system can offer an effective filtration for your tank.

Its filtration system makes use of innovation. It has anaerobic bacteria to remove nitrate and ammonia effectively, allowing for maximum tank oxygenation.

It also involves an activated carbon cartridge that’s able to get rid of toxins, chemicals, discoloration, and odors, among other contaminants in your tank.


  • Quad Filtration System
  • Quietly operates
  • Adjustable flow knob
  • Removes harmful chemicals
  • Both freshwater and saltwater applications


  • It is only suitable for tanks up to 20 gallons, so there’s no room for upgrading

Best Filter For 20-Gallon Tank Buyer’s Guide

Before diving straight into an impulse purchase situation, there are numerous factors that you should consider such as type, size, and filtration. Read our helpful Buyer’s Guide below for advice on what to look for while you’re shopping around. 

Type of Filter

There are three different types of fish tank filter that we recommend for 20-gallon fish tanks. These are a hang on back filter, the internal filter, and the canister filter.

We won’t be covering sponge filters here as although they are very effective in smaller fish tanks, they are not suitable for larger aquariums. Therefore, we do not recommend using sponge filters in fish tanks that are bigger than 10 gallons.

Hang on Back (HOB) Filter

HOB filters are extremely popular as they are considered ideal for beginners due to how easy they are to use. Also known as Power Filters, all of their components are self-contained, and users simply just need to hang them on the back of their fish tank.

The HOB filter’s internal pump draws water from the aquarium and runs it through the filter’s integrated cartridge, which contains the materials necessary to purify the water.

HOB filter’s internal workings may vary slightly, but they by and large involve the same methods of filtration. This filter might be one of those that you can typically see in many households.

It works effectively and can offer versatility, as it can help in aspects that include chemical, mechanical, and biological.

Internal Filter

Internal filters are placed entirely inside the fish tank and are fully submersible. This can be an advantage as this allows you to place your aquarium wherever you want because there will be no bulky parts poking out of it.

An internal filter works differently than a hang on back filter. But the main idea is the same, it will clean the water inside the tank if it’s used correctly.

Though it’s worth mentioning that most internal filters are made for smaller aquariums. We recommend checking with the manufacturer beforehand to confirm that your filter is suitable for a 20-gallon tank.

Canister Filter

Canister filters tend to be more expensive than the previous two options, but they’re praised for their durability and quality. This filter can support three-way filtration, including chemical, biological, and mechanical filtration.

It includes a siphon tube that takes the water inside while simultaneously filtering it. This filter also has a separate tube that works by returning the water while controlling the current or water movement.

If these features are important to you, it could be worth splashing out on a canister filter. This filter also has to be placed outside the aquarium, so more space is needed when compared to the previous internal filter.


Gallons per hour or ‘GPH’ It’s the measure of how much water the motor in a filter can pump in an hour. It’s typically recommended that your filter should have a GPH equal to four times the volume of your tank.

So, for a 20-gallon tank, you would want a filter with a GPH of at least 80. However, we recommend always opting for a higher GPH whenever possible. The more water gets pumped through the filter, the more efficiently waste is processed.


You can find relatively small filters for 20-gallon tanks. Slim profiled filters are a great choice because they don’t occupy much space. It’s important to remember, the bigger the filter the more space you’re going to need to house it.

With this said, you could save more space to decorate your tank.  There will also be more room for your fish to swim freely. You also may want to take a look at a hang on back filter or HOB because it offers ample space for your fish and decoration.


It’s a good idea to invest in a self-priming filter system. This means that even if you experience a power cut or have to clean the tank, it will automatically turn itself back on afterward. They require less attention than a non-self-priming filter system.

Filtration process

It’s a good idea to look out for filters that work thoroughly to ensure that it can keep your tank clean. Also, you should choose a filter that works for your schedule and at your convenience. 

Best Filter For 20-Gallon Tank - Frequently Asked Questions

Are filters expensive?

A canister filter will be the most expensive option. Most HOB filters rest in the $20-$30 range, while canister filters can often cost over $100, sometimes even exceeding the $300 mark.

This is, of course, directly related to the increased functionality, versatility, and power that you get when using a canister filter in comparison to a power filter (which has greater ease of use, but much less concerning features).

What’s the purpose of a tank filter?

As time goes by, the water in your fish tank will start to become dirty. The denizens of your tank, mainly fish and turtles, will excrete waste, particles of food will build up, and various toxic compounds that are harmful to your aquarium community will increase.

To remove these from the tank environment, a strong filter that uses the 3-stage process (it combines mechanical, biological, and chemical means of purifying water) is the best option. Both canister filters and Hang On Back (HOB) filters are capable of this level of water filtration.

What’s the best kind of filter?

There is no single filter that fits every aquarium need. Typically, HOB filters work well for beginner aquarists because they provide all three types of filtration – mechanical, biological, and chemical.

Most models use drop-in cartridges, making them very user friendly. Internal filters go inside the aquarium, allowing users to place the aquarium where space is limited.

Canister filters can be loaded with virtually any filter media, making them the most versatile type of filter. They take a little more time and effort to service but do not require cleaning as often as other types of filters.

Tanks with messy fish should have good mechanical filtration, while heavily populated aquariums should have extra biological media. To ensure optimal performance, choose a filter rated one size larger than your aquarium.