Published: April 27, 2021 - By: - Categories: Equipment

Filters are an essential piece of hardware in nano tanks of 5 gallons or less. The small volume of water in these tanks means effective filtration is extremely important to the health of your livestock. Here you can find information on a variety of makes, models, and types of filters to help you choose a good quality and reliable option.

Best filters for nano fish tanks up to 5 gallons

Model Our rating Type Flow rate Ideal for Media
Aqua Clear 20 power fish tank filter editor's ratingAqua Clear 20 power fish tank filter Hang-On-Back 100 GPH, adjustable 5-20 gallons Foam, Activated Carbon, and BioMax
Azoo Mignon 60 Power Filter editor's ratingAzoo Mignon 60 Power Filter HOB 16 GPH, adjustable up to 3.5 gallons filter pads
Penn-Plax Small World Aquarium Filter (SWF1) editor's ratingPenn-Plax Small World Aquarium Filter (SWF1) internal filter air pump powered (buy separately) up to 5 Gal Bio Sponge, Carbon, and Zeolite
Marina S10 Power Filter editor's ratingMarina S10 Power Filter HOB 55 GPH, adjustable up to 10 gallons filter cartridges with included carbon & zeolite
Aquatop Classic Aqua Flow Sponge Filter CAF-10 editor's ratingAquatop Classic Aqua Flow Sponge Filter CAF-10 Sponge filter air pump powered (buy separately) up to 10 Gal sponge
Aqueon Quietflow E Internal Power Filter editor's ratingAqueon Quietflow E Internal Power Filter internal filter 25 GPH up to 3 gallons carbon cartridge
Finnex Pure-5 Power Aquarium Filter editor's ratingFinnex Pure-5 Power Aquarium Filter HOB 30 GPH, adjustable up to 5 gallons 1 pcs filter cartridge included
Marina I25 Internal Filter editor's ratingMarina I25 Internal Filter internal filter up to 6.6 gallons (25 L) filter cartridge with included carbon & zeolite
NO.17 Submersible Aquarium Internal Filter 6W editor's ratingNO.17 Submersible Aquarium Internal Filter 6W internal filter 132 GPH (500 L/H), adjustable 1-10 Gal sponge
Tetra Whisper 4i Internal Filter editor's ratingTetra Whisper 4i Internal Filter internal filter 27 GPH 4 Gal small Bio-Bag cartridge

Small aquarium filter reviews

Aqua Clear 20 power fish tank filter

The more time your aquarium water spends in contact with your filter media, the cleaner it’s going to be. With this in mind, AquaClear has designed this power filter to use 3 different media, providing chemical, mechanical, and biological filtration to preserve beneficial bacteria.

This unit has excellent filtration volume and ensures that the water surface remains broken, which is essential for introducing available oxygen to the system. This model also features adjustable flow control that gives the aquarist greater control of the environment to suit the biotype and species in their aquarium.

Azoo Mignon 60 Power Filter

The Azoo Mignon 60 Filter is ideal for the nano fishkeepers out there. This filter has a compact, attractive design, and super quiet, energy-efficient performance. It is important to consider the flow rate of your filter when setting up a small aquarium, especially for fish like bettas that don’t enjoy a strong current. To make your life easier, this filter has an adjustable output that can be easily adjusted with a dial.

Azoo Mignon filter componentsAzoo Mignon filter components

Not only is the output adjustable to safe levels, but the design of this filter also ensures that the intake is safe. Small livestock and weaker swimmers can easily be sucked into a powerful filter or become stuck on the intake, but this unit comes with a handy prefilter sponge that fits securely over the intake, meaning your livestock will be safe.

Azoo Mignon filter media detailAzoo Mignon filter media detail

The Azoo Mignon 60 Power Filter comes with 2 easy to replace filter pads, for mechanical and biological filtration, but you can also easily custom fit your own filter media into the chamber. Just be sure not to overfill the compartment with a dense medium as this could put extra strain on the built-in motor.

 Penn-Plax Small World Aquarium Filter (SWF1)

The Penn-Plax Small World aquarium filter is an extremely compact internal air-powered filter that works well in a variety of tank shapes, including rounded designs and bowls. This unit is specifically designed for use in small aquatic habitats and tanks of up to 5 gallons.

Penn-Plax Small World Aquarium Filter side viewPenn-Plax Small World Aquarium Filter side view

Being an internal air-powered filter, you will need a small air pump and some airline tubing, which are sold separately, to operate this filter. This model is suitable for both acrylic and glass tanks and can be used in both fresh and saltwater. The green and clear plastic design of this filter does not stand out strongly and works especially well with natural green aquascapes.

The Penn-Plax Small World Aquarium Filter includes a disposable filter media cartridge with carbon and zeolite crystals, as well as a bio sponge, ensuring that effective biological, chemical and physical filtration takes place.

Penn-Plax Small World Aquarium Filter suction cupsPenn-Plax Small World Aquarium Filter suction cups

This filter is very easy to install, using the 2 suction cups on the filter mounting bracket. The strength of the current created within your aquarium will depend on the size of the air pump used and it is a good idea to use a bleed valve or an airline control valve to adjust the flow.

Marina S10 Power Filter

The Marina S10 Power Filter is one of the best hang-on-back (HOB) filter options for fishkeepers with limited space around their tanks. This great-looking filter is suitable for tanks of up to 10 gallons and has a fully adjustable flow to suit the size of your aquarium, and the kinds of fish and animals you keep.

Marina S10 Power Filter top viewMarina S10 Power Filter top view

The Marina S10 Power Filter comes with a bio-clear and bio-carb filter, which are very easy to replace, saving you time and effort on maintenance. Being a hang-on-back (HOB) filter, this unit takes up very little space inside your aquarium and it has an innovative design that incorporates the motor on the inlet pipes, meaning the motor is housed under the water surface for quieter operation.

Marina S10 Power Filter cartridgesMarina S10 Power Filter cartridges

This is a self-priming filter which means you don’t have to fill the compartment before restarting the unit after a power failure. In order to protect your livestock, this model includes a prefilter sponge which means small animals won’t become trapped within the filter during operation.

Aquatop Classic Aqua Flow Sponge Filter CAF-10

The Aquatop Classic Aqua Flow Sponge Filter is a simple but effective internal air-powered filter for a Betta, or shrimp and snail tank that needs low water flow. This filter provides mechanical and biological filtration and has the added benefit of increasing oxygen levels in your tank.

In order to run this filter, you will need a small air pump (buy separately) and a length of airline hose. This style of filter does not produce any strong suction that could trap or injure your fish or livestock. Although the sponge of this filter provides plenty of surfaces for beneficial bacteria to colonize, it is also possible to add a further filter media of your choice to the compartment for customized filtration.

Aqueon Quietflow E Internal Power Filter

The Aqueon Quietflow E Internal Power Filter can be hung from the rim of your aquarium in a similar way to hang on back (HOB) filters or simply attached to the inside of your tank using the suction cups. Once installed, the unit can be left to run and will automatically restart after power interruptions.

As is indicated by its name, this filter is very quiet and economical with power consumption. The carbon cartridge used provides effective chemical filtration, while beneficial bacteria colonize the sponge for vital biological filtration. This is a great option for nano tanks of up to 3 gallons.

Finnex Pure-5 Power Aquarium Filter

The Finnex Pure-5 Power Aquarium Filter is a hang-on-back (HOB) power filter that can effectively filter up to 30 gallons per hour, although the flow rate is adjustable, meaning you have the power to dial it in to suit your needs.

This filter has extendable intake tubes and is suitable for both freshwater and saltwater tanks. The included carbon cartridge and sponge provide mechanical, biological, and chemical filtration, and are easy to change.

Marina I25 Internal Filter

The Marina I25 Internal Filter is suitable for use in aquariums up to 6.6gallons. The unit is easily installed with the provided suction cups, and once running, will effectively filter your aquarium through biological, mechanical, and chemical action.

This 3 stage filtration process makes use of zeolite and carbon to ensure, safe, crystal clear water without any unpleasant odors. The filter cartridges are quick and easy to replace and one of the great benefits of compact internal filters like the Marina i25 is the very low noise levels created since the motor is submerged.

NO.17 Submersible Aquarium Internal Filter 6W

The NO.17 Submersible Aquarium Internal Filter is highly corrosion-resistant, making it suitable for use in both fresh and saltwater aquariums. The unit is capable of filtering an impressive 132gph but is adjustable to reduce the flow rate.

By attaching a short length of hose to the filter’s output nozzle, you can add aeration to the output. This has the effect of reducing the flow rate further and increasing oxygenation in your tank.

Tetra Whisper 4i Internal Filter

TheTetra Whisper 4i Internal filter by Tetra is suitable for nano aquariums of up to 4 gallons. The flow rate of this aquarium is fixed at 27gph which is not overly strong and the unit is attached using the supplied suction cups.

This filter produces very low noise levels and makes use of both cartridge floss and ultra-activated carbon to provide both mechanical and chemical filtration

How does a filter work?

Filters are designed to clean the water in your fish tank, to keep it clear, odorless, and safe for your fish and plants to live in. Filters work by pushing water through filter media in order to clean it before returning it to the tank. There are 3 basic types of filtration that modern fish tank filters use.

Biological filtration

Biological filtration is probably the most important type of filtration for your aquarium. Even though the water in an aquarium may look crystal clear, if it has not been cycled, it may be very harmful to the fish that live in it. In a correctly established and cycled fish tank, beneficial bacteria will colonize the sponge in your filter and work to change harmful ammonia and nitrites in the water into harmless nitrates.

Mechanical Filtration

This type of filtration involves the physical removal of particles like fish waste in the water. These particles will collect in your filter over time and can be rinsed out of your filter media or you can replace disposable filter cartridges.

Chemical filtration

Substances such as activated carbon and zeolite are also often included in aquarium filters. These materials are able to trap and neutralize harmful chemicals such as ammonia and chlorine in the water to provide a safer environment for your fish and other livestock.

Frequently Asked Questions

Do I need a filter for my betta?

All fish require filtered water to stay happy and healthy in home aquariums. While some experts are able to keep their water clean without electrically powered filtration, this is not recommended for beginners, especially not in the small aquariums that bettas are usually kept in. At the end of the day, all responsible fish keepers should care for the health of their livestock and even though bettas are tough fish that can live for some time without a filter, you should use one in your tank.

Do I need to do water changes if I have a filter?

With a small aquarium, you should get into the habit of doing partial water changes every week. Provided you have not overstocked your aquarium, weekly water changes of around 25% are advised because your filter can not remove all the waste in your tanks.

Do I need to clean my filter?

Over time, your filter media will become clogged by waste and particles in the water. Many power filter models incorporate disposable filter cartridges that should be changed at the frequency advised by the manufacturer.

You should not replace all of your filter media at once as this will remove the beneficial bacteria that are essential for biological filtration. Reuseable filter media such as sponges should be rinsed in tank water that you have removed during a water change to preserve these bacteria.

What flow rate do I need?

Generally speaking, your filter should have an hourly flow rate of at least 4 to 6 times the volume of your aquarium to be effective. Some fish species are adapted to live in strong currents and will enjoy a good flow rate, while fish such as bettas are easily stressed in fast-moving water.

Often it is difficult to keep a low flow rate in very small aquaria and you should select a filter with an adjustable flow rate if keeping fish that do not enjoy strong currents.

Final Thoughts

Perhaps the most important piece of hardware for a healthy fish tank is a quality filter. With so many options out there, choosing the best one for your tank can be difficult. All of the filters in this article make great choices for tanks of less than 5 gallons and if used correctly, will keep your correctly stocked and managed aquarium looking beautiful.

Lucas has been keeping successful fish, planted, and reef tanks for many years. He loves to collect aquatic organisms and keep as many aquariums as he can.

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