It makes no difference whether you have a small or large fish tank; if you do not install an effective filtration device in your aquarium, the water can easily accumulate harmful toxins that could destroy your fish. Have you ever heard of the term “Nitrogen Cycle?” That is essential knowledge for all fish keepers because if you do not properly manage the Nitrogen Cycle in your tank, you will end up with a tank full of sick or dying fish.

We look at the best 20-gallon aquarium filters in this guide, including thorough reviews of our recommended filtration systems to help you make the right choice for a clean tank and safe, thriving pets.

A Brief Comparison of the Best 20-gallons Aquarium Filters.

Product Features
AquaClear Power FilterAquaClear Power Filter Type: HOB Filter
Flow Rate: 100 GPH
Filtration Stages: AquaClear Foam, Activated Carbon and BioMax
Aqueon Medium Filter Quietflow InternalAqueon Medium Filter Quietflow Internal Type: Internal filter
Flow Rate: 130 GPH
Filtration Stages: Filter cartridge, Sponge, Biological
Aqueon QuietFlow LED Pro Aquarium Power FilterAqueon QuietFlow LED Pro Aquarium Power Filter Type: Internal Filter
Flow Rate: 100 GPH
Filtration Stages: 5-stage multi-media filter system
Fluval 106 External FilterFluval 106 External Filter Type: External Filter
Flow Rate: 145 GPH
Filtration Stages: 3-stage filtration system
Penn Plax Cascade Canister Filter 500Penn Plax Cascade Canister Filter 500 Type: Canister Filter
Flow Rate: 115 GPH
Filtration Stages: 3-stage filtration system
Tetra Whisper Power Filter For Aquariums 3 in 1Tetra Whisper Power Filter For Aquariums 3 in 1 Type: HOB Filter
Flow Rate: 210 GPH
Filtration Stages: 3-stage filtration system
Marina Power FilterMarina Power Filter Type: HOB Filter
Flow Rate: 92 GPH
Filtration Stages: 3-stage filtration system

Multiple 20-Gallon Filter Types

There are several different filter systems, and we’ll go through them in more detail below. But first, let’s take a look at how filtration systems operate.

Filtration System Components
The three methods of water filtration are as follows:

Filter Types

The following are the most popular types of filtration systems:

The Advantages of Using a Filter in a 20-Gallon Aquarium.

A 20-gallon or 25-gallon aquarium is a common tank size for beginners because it is large enough to provide an entertaining and impressive show of fish and plants while not being so large that maintenance is excessively time-consuming. However, if your 20-gallon tank lacks an adequate filter system, it will not remain a safe and healthy environment for your fish.

There are some significant advantages of using a filter system for such a small fish tank:

Water Quality

All living things, including fish, invertebrates, and mollusks, generate waste. The waste decomposes over time, releasing harmful toxins into the tank water. Without an effective filter device, your aquarium can easily degrade into a poisonous broth that will poison the fish and other tank occupants.

While weekly partial water changes can help to reduce waste levels in the water, a biological filtration device regulates and manages the Nitrogen Cycle, removing ammonia and nitrites from the water and converting them to less volatile nitrates. Plants use nitrates as fertilizer, which helps to eliminate some of these compounds from the water, while the daily partial water adjustments will take care of the rest. Nitrate levels in your tank should ideally be less than 20 ppm, whereas ammonia and nitrite levels should be nil.

Oxygenation of the Water

Fish require oxygen, which they obtain from the water from their gills while expending carbon dioxide as they breathe. During photosynthesis, living plants absorb carbon dioxide from the water and expel oxygen back into it. That sounds fantastic, but many fish species need well-oxygenated water to survive, and a powerful mechanical filtration device can aid by forcing air bubbles into the water and agitating the water surface to provide the fish with the extra oxygen they need.

Tank Servicing.

Vacuuming the gravel in your aquarium should be part of your weekly maintenance routine. However, by eliminating most of the floating particulate and detritus that would otherwise find their way into the substrate, an effective filtration device will help to lighten your workload. As a result, you’ll need to clean the filter media in tank water about once a month to remove excess sludge that would otherwise clog the system.

Considerations Before Purchasing a Filter for a 20-Gallon Tank

When selecting a filter for a 20-gallon aquarium, there are many important factors to consider:

Size of Aquarium.

A filtration device with a GPH rating of at least 80 gallons is needed for a 20-gallon aquarium. This ensures enough water flow across the tank. When selecting a filtration device, the shape of the tank must also be considered.

For example, if the tank is tall and hexagonal in shape, you don’t want a bulky box-style filter taking up precious swimming space that your fish might be using and ruining the overall appearance of the aquarium. In that case, a hang-on-back filter can be preferable.

Filter Priming

Priming is the method of preparing your filter for use. Priming aquarium filters usually entails loading the filtration unit with water to get it up and running. If you don’t prime the system, it will run with air instead of water in the tubing. This can cause the system’s motor to burn out, the device to fail to properly filter your aquarium water, and the system to become extremely noisy.

While priming your filtration device is usually fairly simple, if you don’t want to deal with the hassle, it’s worth noting that you can purchase self-priming or no-prime filter systems. In that case, drawing water is normally as simple as pressing the primer button a few times.

In the case of a device that requires priming, however, all that is needed is to fill the unit’s reservoir and then run the pump to pull the water through the tubing. After that, the machine is ready for use.

Maintenance
Both filter systems necessitate some level of maintenance to function properly and prevent water chemistry issues. The level of maintenance needed varies depending on the type of device. Beginners often make the mistake of cleaning the filter media too frequently or too thoroughly, which kills the beneficial bacteria that live on the filter media and can cause the tank to re-cycle.

Reviews of the Top 7 Best 20-Gallon Aquarium Filters.

1.AquaClear Power Filter.

AquaClear Power Filter

Type: HOB Filter
Flow Rate: 100 GPH
Filtration Stages: AquaClear Foam, Activated Carbon and BioMax

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Aquaclear aquarium filters are among the most common and high-quality aquarium filters available. Not only is the filtration efficiency good, but the filters are exceptionally well-made and have been known to work without issue for more than a decade.

The Aquaclear is incredibly silent, as long as you manage it properly and keep the water level in your tank topped up. I have one of these filters running in a tank in my workroom, and I can attest that it is extremely silent. In reality, I believe my fish produce more noise than this filter!

One minor annoyance that some users have mentioned is that the flow rate of the pump can be variable. However, as long as you clean the impeller every couple of weeks, this is usually not a concern.

AquaClear Power Filter Pros & Cons
  • When compared to many other similar units, it is reasonably priced.
  • Simple to clean and maintain.
  • In general, they are dependable and long-lasting.
  • It’s extremely quiet.
  • If the impeller is not cleaned regularly, the flow rate would be variable.

2. Aqueon Medium Filter Quietflow Internal.

Aqueon Medium Filter Quietflow Internal

Type: Internal filter
Flow Rate: 130 GPH
Filtration Stages: Filter cartridge, Sponge, Biological

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The Aqueon Medium Filter is a type of medium filter. Quietflow’s Filters employs a four-stage filtration system that involves mechanical, biological, chemical, and stationary wet-dry filtration to keep your aquarium water crystal clear and stable for your fish. The unit’s high flow rate ensures a high level of dissolved oxygen in the water, resulting in good, lively fish.

The pump is designed to operate quietly, and an ingenious feature ensures that it restarts automatically after power outages or cleaning. The filtration device can be used in both freshwater and saltwater tanks.

The main disadvantage of this product is that it needs filter cartridges, which must be fully replaced every four to six weeks.

The machine comes with a lifetime warranty.

Aqueon Medium Filter Quietflow Internal Pros & Cons
  • The process is quiet.
  • Freshwater and saltwater will coexist.
  • In general, they are dependable and long-lasting.
  • Guaranteed for life.
  • Filter cartridges are costly to replace.

3. Aqueon QuietFlow LED Pro Aquarium Power Filter.

Aqueon QuietFlow LED Pro Aquarium Power Filter

Type: Internal Filter
Flow Rate: 100 GPH
Filtration Stages: 5-stage multi-media filter system

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This Aqueon filter, like all Aqueon filters, is extremely well-made, quiet, and dependable. There’s also a helpful LED indicator light that indicates when the filter cartridge is clogged and needs to be changed.

Since the filter pump is self-priming, there is no need to worry about getting the machine up and running. The pump is very efficient, and it contributes to a good flow rate for good water oxygenation, which benefits your fish.

The clever five-stage filtration system keeps the water clean and clear, allowing you to see happy, healthy fish. The first filter eliminates large waste particles, while the second step uses activated charcoal to eliminate discoloration and chemicals. The third stage is the biological component of the system, the fourth stage introduces oxygen, and the optional fifth stage removes any residual pollutants such as phosphates.

Aqueon QuietFlow LED Pro Aquarium Power Filter Pros & Cons
  • It starts automatically.
  • Filtration in three stages.
  • The internal pump reduces noise and eliminates leaks.
  • Deficient durability.

4. Fluval 106 External Filter.

Fluval 106 External Filter

Type: External Filter
Flow Rate: 145 GPH
Filtration Stages: 3-stage filtration system

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The Fluval 106 Canister Filter is no exception to Fluval’s reputation for delivering high-quality goods at reasonable prices.

Because of its design, the filter has a higher capacity than similar-sized filters. The configuration of the device allows for two media baskets, one for biological filtration and one for chemical filtration. The device also allows for some customization, as you can switch out the carbon and replace it with something else if you prefer.

The flow rate can be adjusted, which is great if you have fish that prefer slower water. The device includes an instant primer for fast priming, and special noise reduction technology keeps the machine running quietly and unobtrusively.

An intake strainer and a mesh guard help to reduce the amount of debris that enters the filter. That means your tank will be washed more effectively, and machine maintenance will be simpler and less time-consuming.

Fluval 106 External Filter Pros & Cons
  • The process is very quiet.
  • Filtration device with three stages.
  • Easy to keep up with.
  • As compared to other filters, it is expensive.

5. Penn Plax Cascade Canister Filter 500.

Penn Plax Cascade Canister Filter 500

Type: Canister Filter
Flow Rate: 115 GPH
Filtration Stages: 3-stage filtration system

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The filter media is housed in two wide, stackable containers in the Cascade Canister Filter. While you can use Cascade’s own media, it can be very costly, and there are less expensive alternatives.

You can also customize the water return process by using either the standard return chute or the spray bar, all of which are included with the device.

The device does need some setup before it is ready to use, and you must prime the canister by pressing the primer button a few times. When you plug in and switch on the device, you can hear some air noises before the air is cleared from the unit. However, once the machine is up and running, it is incredibly quiet.

The device is simple to keep up with. Close the water shut-off valves on the two hoses and remove them from the canister’s roof. To access the media trays inside, remove the canister cap, replace or rinse the media, and reassemble everything.

Penn Plax Cascade Canister Filter 500 Pros & Cons
  • The operation is very quiet.
  • Filtration media that can be customized.
  • Simple to keep up with.
  • The cost of filter media is high.

6. Tetra Whisper Power Filter.

Tetra Whisper Power Filter For Aquariums 3 in 1

Type: HOB Filter
Flow Rate: 210 GPH
Filtration Stages: 3-stage filtration system

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The Whisper 3 in 1 Power Filter could be the right option for you if you’re looking for a good filtration device that does the job without breaking the bank. The unit is well-constructed, with long-lasting components. The flow is adjustable, and the spillway oxygenates the water by agitating the surface. While the filter media isn’t of the highest quality, it does provide a lot of surface area for beneficial bacteria to grow on.

The motor is extremely quiet, so you won’t be bothered if you keep the machine in your bedroom or workspace. Furthermore, since there are no moving parts in the machine, there is a very low risk that it will fail you. Overall, the Tetra Whisper is a good product.

Tetra Whisper Power Filter Pros & Cons
  • The process is quiet.
  • Cost-effective.
  • The process of priming itself.
  • Filter cartridges are supplied.
  • Biological filter media of poor quality

7. Marina Power Filter.

Marina Power Filter

Type: HOB Filter
Flow Rate: 92 GPH
Filtration Stages: 3-stage filtration system

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The Marine Power Filter is a compact device that attaches to the back of your aquarium. The pump motor is located on the intake side of the tank, and the media is housed inside a clear plastic HOB assembly. Since the motor is submerged, you don’t have to prime it every time you unplug it, and the filter height is adjustable to accommodate different water levels. The motor is also very quiet.

The device has an adjustable flow rate, allowing you to tailor the speed of the water movement to your livestock’s needs. The flow is often guided horizontally so that your fish are not buffeted when swimming, and the flow direction helps to agitate the water surface.

The device comes with two Bio-Carb and two Bio-Clear filter cartridges, all of which contain Cermitek biological filter media.

Marina Power Filter Pros & Cons
  • Flow rate can be adjusted
  • Simple upkeep
  • Running at a whisper-quiet level
  • The flow rate could be higher.

Final Thoughts

I hope you considered my article on the best filter for a 20-gallon tank to be useful and insightful.

The Aqueon QuietFlow LED Pro Aquarium Power Filter is our favorite of all the items we looked at.

This high-quality filtration device is dependable and well-made for long-term use, and it includes a useful LED indicator light that indicates when the cartridges need cleaning or replacement. The pump is extremely quiet, and the five-stage filter media system keeps the water crystal clear and stable for your fish.

Newcomers to the hobby on a tight budget can prefer the Aqueon Medium Filter Quietflow. Internal filter with four stages of filtration for clean water, an efficient flow rate for good oxygenation, and silent operation, all at an affordable price.

William
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