5 Best Filter for 20 Gallon Aquariums

The 20-gallon tank is an excellent mid-sized aquarium for intermediate aquarists. You can keep around 15 fish in this setup if you are especially interested in having a community aquarium.

Best Filter for 20 Gallon Aquariums

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Best Filter for 20 Gallon Aquariums

These residents need a pristine environment to live, which is why you need a powerful filter for your 20-gallon tank. We selected five filters that are guaranteed to help you maintain a healthy aquarium, and they are:

1. Aqua Clear HOB Filter

This filter promises the longest contact time with filter media when compared to similar models in the market. The refiltration system makes the filter very efficient and reduces operating costs.

You can easily control the flow rate while still maintaining the filter’s filtration efficiency. Aqua Clear also guarantees a filtration Volume that is seven times that of comparable filters with this model.

It is suited for aquariums between 10 and 30 gallons, and it will work perfectly with your 20-gallon tank.

This hang-on filter system is positioned on top of the tank, where it filters water via a silent waterfall. The simplicity of the filter’s design will resonate with many aquarists since all you need to do is clip it on the back of the tank. A tube will subsequently pump the water from the aquarium and into the tank.

While the filter provides all three levels of filtration, it especially delivers on biological filtration. It comes equipped with BioMax, Cycle Guard, Activated Carbon, and Aquaclear Foam for superior biological filtration.

These bio-media components are designed to get rid of such toxic elements as ammonia and nitrates. They will also allow beneficial bacteria to develop colonies for advanced filtration.

The filter is packaged with the filter media inserts, filter case, media tray, U-tube, in-pick strainers, and a lid. One advantage of the device is it comes with a 2-year warranty.


2. Fluval C Power Filter

The Fluval C Power Filter is rated for gallons of up to 30 gallons. It boasts a flow rate of 119 gallons per hour, which is guaranteed to leave your tank fresh and clean. It is designed to offer an optimal surface area and maximum dwell times in the different filtration stages.

The filter presents a five-stage filtration system, where the first stage includes mechanical filtration with a Poly/Foam Pad. The pad has a large surface area to perform two stages of mechanical filtration. Large particles are trapped in the first stage and fine debris in the subsequent level.

The filter includes an Activated Carbon insert made from 100% top quality and research-grade carbon. The insert’s large surface area helps with the absorption of impurities. It will remove discoloration and odors to give you a crystal-clear tank.

A Bio-Screen and C-Nodes perform biological filtration. The screen is positioned on top of the filter’s Trickle Chamber cover, and it extracts any debris left in the water before it gets to the biological chamber.

If further ensures that the water is evenly distributed before dripping into the filter’s C-nodes. The motion of the water mimics the sound of rain. The C-Nodes are characterized by a complex pore system that offers a large and conducive environment for bacteria to thrive.

These bacterial colonies remove nitrites and ammonia and leave your water healthy. The nodes are organized in a star-shape to offer a larger surface area in comparison to traditional cartridges.

The device’s refiltration system lets the fish owner regulate the flow rate, which is especially handy for delicate fish and plants that need gentle currents. Reducing the flow rate will not affect the filtration efficiency, and you will still get a healthy tank.

This clip-on filter is also easy to clean and maintain. It comes with a cleaning indicator to let you know when to clean the polyfoam. The filter is packaged with everything you need to set up, including a leveling device, telescopic intake tube, mechanical frame, chemical basket, impeller, and a motor unit with a seal ring.


3. MarineLand Magnum Polishing Internal Filter

This canister filter is suited for aquariums of up to 97 gallons, and it is designed to filter 290 gallons per hour. This processing power will give you quality water that is free from any harmful elements. Its efficiency will keep your 20-gallon setup clean and clear by keeping up with the waste-production rate of your aquatic pets.

In addition to the three filtration levels, the filter also provides water polishing.

A Rite-Size floss sleeve performs mechanical filtration by trapping dirt and debris. For chemical filtration, MarineLand has equipped the filter with Black Diamond Premium Activated Carbon. It will remove discoloration, odors, and other impurities. For consistent results, the carbon should be replaced every month.

Biological filtration is promoted by a surface area of 153 square inches, which encourages the growth of Bio Spira. This bacterium ensures that there are no nitrites or ammonia in the tank’s water.

The filter also has a water polishing feature in the form of a reusable pleated micron cartridge to remove fine debris. You can charge the cartridge with diatomaceous earth to boost its filtration efficiency.

One winning feature with this filter is its dual filtration chambers. A fish owner can customize the kind of media they want to use as well as their amounts. Depending on the needs of your aquarium system, you can stack on one type of media, or even reduce another. This versatility makes the filter especially attractive.

The filter also scores favorably when it comes to maintenance and usability. It comes with suction cups to fit in the walls of your tank. The motor is self-priming, and you only have to submerge it, and it is good to go.

Overall, this filter is a solid buy for a 20-gallon tank.


4. Penn Plax Aquarium Cascade Canister Filter

The Cascade 500 filter works with aquariums of up to 30 gallons at a flow rate of 115 GPH. It is made of hard plastic for optimal durability, and installation is a breeze. The filter comes with all the necessary accessories to install, and it will start filtering water in about 30 minutes.

It features a self-priming button to kickstart filtration, and Penn Plax promises that you will see clearer water in less than a day. You do not need to siphon water into the canister with this model manually. Penn Plax advises aquarists to push down the button for five to ten minutes to trigger the filtration process.

The filter also includes several other noteworthy features. Its flow valves rotate 360 degrees to be able to fit even in tight aquarium cabinets. It has large capacity media baskets to allow for customization on the part of the aquarist.

You can use any combination of media that you require, including activated carbon and bio-sponges. No impurities will pass through the large filter trays. It utilizes directional returns to suspend impurities so that they can be taken in by the filter.

This model is incredibly easy to operate and maintain. Its swimming-pool style hose clamps and flow-rate control valves make installation and adjustment hassle-free. The seal is air-tight to assure appropriate flow-rate and encourages quiet operation.

The filter has shut-off valves on the hoses attached to the canister. During cleaning time, unscrew the valves and pop open the top to access the media trays. The valves are well-secured to prevent any leaks.

It also has a sturdy tip-proof base to keep it in place. The easy-lift alignment will release vacuum suction to make maintenance easy.


5. Finnex PX-360 Compact Canister Filter

The Finnex PX-360 canister filter boasts a vacuum-tight force filtration process that is superior to conventional power filters. Finnex promises aquarists a clearer and cleaner aquarium with this model. This versatile filter is small but powerful, and it will suit your 20-gallon setup.

You can use it a canister filter, or use the accompanying brackets to hang it on the back. Also included is a spray bar to spread the water flow across the aquarium, or you can use a spray nozzle for a more powerful flow. Its motor is capable of rates of up to 95 GPH for high-quality water.

The filter allows for three filtration stages, and it is equipped with the necessary media. You get activated carbon floss, ceramic rings, and a sponge strainer. Since the container is translucent, you will be able to see all the waste that gets trapped by the media and schedule cleaning times.

Among the advantages of this filter is its compact design. You can either place it next to the aquarium or clip it onto the tank. It is impressively lightweight, and it will, therefore, place little pressure on your tank. The filter also rates highly for quiet operation.

Reviewers commented on the durability of the Finnex PX-360, which is made from sturdy ABS material. Finnex provides a 180-warranty with this model.


How to Choose a Filter for 20-Gallon Aquarium?

The 20-gallon tank is incredibly versatile, and it should be maintained appropriately. The first decision in selecting a filter for a 20-gallon tank is the type that you will get.

Some aquarists will go for the hang-on-back filter, which is simply clipped onto the back of an aquarium. A lift tube will then channel water from the tank and into the filtration chamber. The water flows across the media inserts and back into the aquarium.

Another filter to consider is the internal filter, which is fully submerged into the fish tank. These filters are relatively hard to clean and maintain, and they are not as efficient as HOB models.

Canister filters are the most powerful of the three, and water is pressurized through the media. While they are commonly designed for larger aquariums, some are rated for medium-sized tanks like 20-gallons setups. Canister filters are positioned outside the tank, where they generate more noise than the other two kinds of filters.

Other considerations to make include:

Filter Maintenance

Every aquarist wants a filter that is easy to set up, clean, and maintain. It should be easy to take apart the components of your choice of filter and access the media trays. Most brands put effort into ensuring that fish owners can put together their filters in several minutes and without a high level of technical knowledge.

Filtration System

The most important feature to look out for in a filter is its processing power, which will be indicated by the filtration stages and flow rates. The Fluval C Power Filter, for example, provides five stages of filtration to ensure that no dirt or debris passes through the media. A good filter should also allow for the customization of media.

The flow rate of a filter will indicate how much water will be processed by the system in an hour. If you keep fish that produce a lot of waste, look for higher flow rates.

How Often Should You Clean Your Aquarium Filter?

Beginner aquarists make the common mistake of cleaning the filter every time they see some debris. The job of the filter is to get dirty while the water gets clearer. Cleaning a filter can be scheduled every month, although it will depend on the kind of setup you have.

To know if it is time to clean the filter, check if the water flow rate has reduced to determine if it has clogged up. You can also clean it if you see a significant amount of sludge or free-floating particles in the water.

Why Oversize Your Aquarium Filter?

Experienced aquarists commonly advise over-filtering by choosing a filter that is rated for a larger aquarium than yours. Smaller filters will clog quickly, especially if your fish produce a lot of waste. Bigger filters are, however, known for higher flow rates, but you can diffuse the current for fragile fish.

What to do if Your Aquarium Filter Stops Working?

Your filter may stop working for a number of reasons, some of which you can repair by yourself. Filters will stop running if their motor, impeller, or intake and outtake tubes become clogged. You may need to unclog the motor using your hands or lightly compressed air.

Power surges can also blow the filter and force you to buy another one. If the damage is extensive, it is always a good idea to consult a mechanic.


In the spirit of over-filtering aquariums, buy a model that is rated for 30 gallons to 50 gallons for your 20-gallon setup. Brands like Aqua Clear, Penn Plax, Finnex, Fluval, and MarineLand have diverse models for a medium-sized tank, ranging from HOB, canister, and internal filters.

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