Choosing the best filter for a 20-gallon tank will not only keep your fish healthy but also serve you for a long time. However, with so many options available in the market, it could be confusing to pick out a filter that suits all your needs.

Moreover, most canister filters offer less efficiency, poor build quality, and inadequate flow rates to maintain a hygienic fish tank.

This is why we pain-tested a dozen aquarium filters and compiled the best options into a list. Our judgment is based on factors such as efficiency, durability, capacity, and a few other criteria to deliver only the best 20-gallon aquarium filters.

We also included a comprehensive buying guide to help you make a worthy purchase for your fish tank. That being said, let’s begin.

Comparison Chart

Product Name Ideal For Tank Size (in gallons) Flow Rate (in GPH) Type of Filter
AquaClear Hagen

20-30 150 Pump
Fluval C2

10-30 153 Pump
MarineLand Penguin

20-30 100 Bio-wheel
Marina S20 20 92 Pump
AQUANEAT Corner Filter

20-40 60 Sponge

Best Filter For 20-Gallon Aquariums – Handpicked Reviews

Here is the list of the best small tank canister filters in the market :

1. AquaClear Hagen Power Filter

Pros:

  • Silent operation
  • Customizable filter media
  • Mechanical and biochemical filtration
  • Adjustable flow rate
  • Simple installation

Cons:

  • Slightly expensive
  • Regular maintenance

AquaClear Hagen hang-on-back filter is a reliable option for anyone looking for a powerful filter for their 20-gallon fish tank. It’s engineered to provide your aquarium with superior water quality and provide easy use for all beginner aquarists.

This filter offers a high flow rate of 150 GPH for fast cleaning. However, if you have a planted tank and require a lower current, you can use its regulator to adjust the flow accordingly. It has a unique waterfall technology that functions silently and does not disturb the water a lot. Moreover, this movement allows for the proper aeration of the tank water, so your fish live freely in crowded tanks.

It uses three multi-stage filter media to provide biological, chemical, and mechanical filtration. And its spacious design allows it to hold six times the media volume than the market standard. It also offers the highest media-to-water contact time for a well-rounded cleaning.

It includes a giant sponge that can handle a large amount of dirt and gunk for mechanically filtering the water. This sponge comes with a pre-filter to make sure that your small fish or shrimps don’t get sucked in. Aside from mechanical filtration, the sponge setup also acts as an ideal site for bacterial colonization. And you can clean it simply by rinsing it every two weeks.

You also get AquaClear’s Biomax media with this filter, which is built to deliver long-lasting biological filtration. This media works by blending a network of fine pores in ceramic rings that provide an increased surface area. It creates the optimal conditions for beneficial bacteria to grow inside your fish tank.

Lastly, the high-grade active carbon fittings offer chemical filtration by removing excess nitrates and ammonia. It also eliminates harmful metals and odors and softens the water to create a stress-free environment for your fish.

Overview:

The AquaClear Hagen is highly trustworthy and durable if you’re looking for a long-term investment for your aquarium. It has a swift and straightforward installation, which is very convenient for beginners. Moreover, it only requires minor routine maintenance every two weeks, which is godsent for office workers.

2. Fluval C Series Power Filter-C2

Pros:

  • Great processing power
  • It helps to aerate the water
  • Special heat dispersion function
  • Cleaning indicator
  • Easy installation

Cons:

  • Slightly loud
  • Requires regular media change

The Fluval C2 filter is a popular choice among aquarists with 20-30 gallon tanks. It is extremely fast and filters out up to 153 gallons of water per hour. In other words, your 20-gallon aquarium’s water will be purified over seven times in a single hour. This filter repeatedly pumps water inside the tank to further improve filtration efficiency.

It follows a 5-stage filtration process for the overall hygiene of your fish tank. This process consists of two stages of mechanical filtration using polyester and foam filter media to catch large dirt particles. For chemical filtration, this filter comes with activated carbon media that removes toxins and odor.

Lastly, it has a dual-phase biological filtration system that utilizes Bio-Screen and ceramic nodes to get rid of harmful bacteria while keeping the good bacteria intact.

Fluval C2 has a robust filtration control system that allows you to slow down the water stream to suit your delicate fish and plants. The inlet pipe is telescopic and offers better flexibility over the flow inside your tank.

Another impressive feature of this filter is its trickle waterfall technology. Similar to AquaClear Hagen, this filter also has a small fountain to provide better airflow for fixing oxygenation issues in your aquarium. It allows your fish to swim freely in congested tanks. Additionally, the trickle cabinet is turbocharged with C-nodes for quick and efficient nitrogen fixation.

If you think all these components will require a lot of maintenance for proper functioning, you can keep your concerns aside. The Fluval C2 filter has an entirely modular architecture that allows you to manage each stage individually for hassle-free routine upkeeping. Moreover, you can simply rinse the foam layer to remove all the gathered dust and debris.

What sets this filter apart is that it follows a unique heat diffusion process that effectively reduces the excessive heat so that it’s not released back into the aquarium.

Overview:

If you are looking for one of the fastest filters, Fluval C2 is a great option to consider. Its five-stage filtration process and a wide variety of helpful features make sure that your aquarium water is crystal clear. Additionally, it is equipped with an indicator that tells you when it’s time to clean the filter, which is a great inclusion for people on a tight schedule.

3. MarineLand Penguin Bio-Wheel Power Filter

Pros:

  • Convenient media change
  • Easy to mount and install
  • Quick maintenance
  • Has features to prevent overheating
  • Compact setup

Cons:

  • It can be a little noisy
  • Needs manual priming

The Marineland Penguin Bio-Wheel Power Filter is a modern and stylish hang-on-back device designed for fish tanks up to 20 gallons in size. This powerful filter can actively clean the water up to five times every hour with its remarkable flow rate of 100 GPH. It has a 3-stage filtration design that provides excellent biological, chemical, and mechanical cleaning.

This filter hosts an extensive rite-size B filter cartridge with 3-stage filtration. There is an additional tab if you want to use a 2nd rite-size B cartridge to further increase the water quality. These cartridges have fine mesh paper, which is ideal for eliminating dirt and fish taste from the water. It also has activated carbon inside, which ensures proper chemical filtration.

Another major benefit of the Marineland filter over other filters is its airy and highly customizable interior. This enables the use of bio-balls, filter floss, and a variety of different filter add-ons that can significantly enhance the environment of your aquarium.

The intake tube of this filter implements the bio-wheel technology that cools down the device through convection currents and avoids overheating. Speaking of which, it has a two-piece ventilated area that helps keep this filter cool and ensures that changing the filter media is as simple as possible.

MarineLand Penguin filter has an adjustable flow rate and a submerged motor with a dampener for reduced running sound levels. It ensures that the filter is running noise-free even after several years of use, making it one of the most silent filters in the market.

When it comes to installing this hang-on-back filter, you can simply clip it to the rear end of your fish tank. The assembly and mounting process take less than two minutes as it is very straightforward. It has a sleek design and lightweight build, and it takes a compact space both inside and outside the tank.

Overview:

The MarineLand Penguin filter is a well-rounded device that can clean your 20-gallon filter with ease. It is available in 75 GPH, 100 GPH, 150 GPH, and 200 GPH variants, and all of them are durable and easy to maintain. It packs excellent performance and a high flow rate, which makes it worth checking out.

4. Marina S20 Power Filter

Pros:

  • Compact design
  • It can fit up to 4 filter media cartridges
  • Silent operation
  • Energy efficient
  • Adjustable flow rate

Cons:

  • Flow rate is less as compared to other options
  • Flimsy structure

If you have a small tank with limited space in your aquarium, the Marina S20 is a great option to consider. Even though it has a compact and lightweight design, you can trust it to deliver proper filtration to your tank water. It has a decent flow rate of 92 GPH and can filter your 20-gallon aquarium up to three times in a single hour.

This filter has a complete see-through design that looks absolutely stunning with aquarium lights. Moreover, the transparent body makes it easy to clean during routine maintenance and identify if anything is clogged.

Like the other filters on our list, the Marina Power Filter also features an adjustable flow rate. This allows you to regulate the flow according to your tank’s needs. Additionally, you can also steer the stream sideways to allow your fish to swim in calm waters, and it can also be used to stir up the surface for improved oxygenation.

Manually priming the filter is not everyone’s cup of tea. Fortunately, the Marina power filter is a self-priming filter, which is always a plus point as it saves you a lot of time and effort.

Furthermore, if you’re looking for a silent filter, we recommend checking out the Marina S20. It has a compact submerged motor, which is one of the best features of this hang-on-back filter. It not only helps to save space but also brings down the noise level significantly.

This filter utilizes a four-stage filtration process that includes chemical, mechanical, and biological filtration. It comes with two bio-clear and bio-carb filter media that are simple to replace during routine maintenance.

Overview:

If you have a compact tank or don’t want to install large devices in your aquarium, you might find the Marina S20 power filter suitable for your aquarium. It has a thoughtful blend of useful features and performance, which is the best you can get at its price point. It’s easy to maintain, and its see-through design makes it attractive to look at.

5. AQUANEAT Aquarium Air Driven Bio Corner Filter

Pros:

  • Easy to set up
  • Energy efficient
  • Silent operation
  • Convenient cleaning
  • Safe for small fish

Cons:

  • No chemical filtration
  • Unaesthetic look

The AQUANEAT Air Driven Bio Corner Filter is an advanced version of a traditional sponge filter, with a decent flow rate of up to 60 gallons per hour. This simple-looking sponge filter is one of the best cleaning devices to pair up with your 20-gallon fish tank.

It has a compact build that is only 4 x 3.25 x 6 inches in dimension. When paired with its corner fitting design, it makes this filter an ideal option for small aquariums. This filter provides both mechanical and biological filtration while also ensuring proper aeration of the tank water.

Since it’s a sponge filter, it works on the principle of differential air pressure. And you can regulate the air pressure in the airline tubing using a gray knob mounted on this filter. Additionally, it allows for double-end flow that helps eliminate dead zones and keeps the water moving for better hygiene.

Moreover, you do not need a separate air diffuser for the AQUANEAT filter to work. It eliminates the need to make any aftermarket purchase while avoiding noise from loud air pumps. An added bonus of this filter is that it consumes the least amount of power on this list, which is a plus point if you’re looking for a budget-friendly option.

The rubber cups used to mount this filter are sturdy enough to provide a firm grip, making the installation straightforward, even for beginners. Maintaining this filter is just as easy as setting it up. All you need to do is attach an air carrier to the mouth of its tube, and rest assured it will clean all the different layers inside this filter.

It is equipped with two large sponges that are very soft and keep your fish safe from being sucked up through the tube. Additionally, it also produces significantly milder currents, making it ideal for planted tanks.

Overview:

If you’re looking to keep small fish such as dwarf cichlids, guppy, and killifish, as well as hatcheries, maternity tanks, and fry tanks, inside your aquarium, this filter is a great option to consider. It has a reliable multi-layer system that can capture even the tiniest dirt particles present in your fish tank.

Buying Guide

Following is a detailed buying guide that will help you pick out the best 20-gallon fish tank filter for your aquarium:

– Size

When buying a filter for your aquarium, it is vital to know the size of your tank. It will help you determine which GPH (gallon per hour) filter rating will best suit your aquarium. An easy way to do it is by multiplying the size of your aquarium (in gallons) by four. This will give you a rough figure of the minimum flow rate required to keep your tank clean.

It is wise to choose an option that can over filter your aquarium, rather than being restricted by a filter that underperforms. The excess flow rate will give you plenty of buffer space to tweak the water stream according to the requirements of your aquarium, and you can even use the filter for bigger tanks as well.

– Priming

Priming simply means preparing your filter for use. Priming aquarium filters typically involve filling them with water to get them up and running. If you don’t prime the unit, it will operate with air instead of water in the pipework. This can make the filter’s motor burn out. Not just that, it may also lead to the unit failing or becoming extremely noisy.

Though priming your filter is usually fairly simple, you can purchase self-priming or no-prime filter systems from our list if you want to avoid the hassle.

– Maintenance

All filter systems demand some level of maintenance in order to function properly and avoid water PH issues. The level of routine maintenance differs depending on what type of system you own. Make sure not to clean the filter media quite frequently or too extensively as it may end up killing the beneficial bacteria that live on the filter media.

Hang-on back filtration systems typically require cleaning in a few weeks, and sometimes the filter media will also need to be replaced. Sponge filters, on the other hand, are very simple to maintain. All you have to do is detach the sponge every two weeks and wash it with water to get rid of the gunk and keep the sponge from getting clogged up.

Canister filters are effortless to clean as well and require your attention only every three to four months. Lastly, filter systems that reside within the tank should be cleaned once a month. For this, you need to remove the filtration media and rinse it in tank water, and then clean the impeller of any excess sludge.

Frequently Asked Questions

To further clear your doubts, we’ve answered some of the most common questions tank owners face.

1. How To Choose A Flow Rate For A 20-Gallon Aquarium?.

In order to determine a correct flow rate for your fish tank, it is essential to first know the size of your aquarium. Once you have that value, multiply it by four. The end figure will be the flow rate (in GPH) required by your aquarium to stay clean.

If you have a densely occupied tank with lots of plants and small fish, particularly with devices such as CO2 diffusers, it is recommended to keep a low flow rate in your aquarium. Whereas some fish like danios and hillstream loaches prefer higher currents and a higher flow rate.

2. How Can I Efficiently Use A High-Flow Filter For My Tank?

Before you purchase an aquarium filter with a high flow rate, it is essential to consider whether it will suit your marine life or not. Even then, we recommend including some hardscape structures in your fish tank. This will help create calm zones where sluggish fish, such as puffers, can flee the high-flow and rest when needed.

3. Do Filters Cause Harm To My Fish?

Filters are critical to the health of the fishes inside your aquarium. They are not harmful as long as you’re not using a filter that generates a powerful current inside your fish tank. In that case, the filter may panic your fish.

Filters with bigger inlets should also have a pre-filter to prevent tiny creatures from getting sucked into the filter or stuck against the air intake.

Final Thoughts

All the filters on our list are excellent choices, so you don’t have to worry about whether they will meet your requirements or not. If we were to choose one, the AquaClear Hagen Power Filter is the best option on our list.

It has a high flow rate of up to 150 GPH, making it ideal for tanks with 20-30 gallon capacity. However, you can adjust the flow according to your needs, which is especially useful for planted tank owners. It has a 3-layer multi-filtration system that ensures mechanical, biological, and chemical filtration for the overall hygiene of your fish tank.

Furthermore, it has a straightforward installation that is very beginner-friendly. You can easily maintain it by simply rinsing it every two weeks. If you are a working individual, we highly recommend going for the AquaClear Hagen Power Filter.

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