BestForPets is reader-supported. Your purchases via our links may earn us an affiliate commission at no extra cost to you. Our Affiliate Disclaimer

The 6 Best Undergravel Aquarium Filters

An under-gravel filter may be precisely what you're searching for if you want to boost the biological filtration in your tank without taking up much room.

Undergravel filters are exactly what they sound like: filters that are installed beneath gravel or another thick substrate. They function by drawing water through the substrate and colonizing helpful microorganisms on its surface.

Undergravel filters that employ carbon filter cartridges are usually biological filters, however they are not necessarily chemical filters.

Undergravel filters perform best when combined with another type of filtration capable of capturing big waste and debris particles.

This will aid in the reduction of waste product buildup beneath or inside the undergravel filter. They operate best in tanks under 55 gallons, although there are a couple that performs well in bigger tanks as well.

BestForPets (bestforpets.org) has taken care of these product reviews to make it easy for you to choose the best undergravel aquarium filters for your tank's size, shape, and waste demands!


Penn Plax Premium Subsoil

We found the Penn Plax Premium Under Gravel Filter System to be the finest overall undergravel filter. This filter is available in five sizes to fit tanks ranging in size from 5 to 55 gallons.

Before purchase, compare the dimensions of the product to the dimensions of your tank to ensure that you obtain a filter that is the proper size to filter your tank and physically fit into your tank.

This filter system contains filter plates that quickly snap together, lift tubes with adjustable height, high pore air stones, and your first set of carbon filter cartridges, which are designed to last 6-8 weeks.

This undergravel filtration system is simple to install, and the filter cartridges are simple to replace, making maintenance a breeze.

The slats in this set’s filter plates are designed to operate with gravel, so they are large enough to enable proper flow without allowing the substrate to slide into the filter.

This kit does not contain an air pump or airline tubing, which must be purchased separately. Make sure you choose an air pump that can handle the amount of the tank. A tiny air pump will not enough for a 50-gallon tank.


  • Available in five sizes ranging from 5 to 55 gallons.
  • Filter plates easily snap together.
  • Lift tubes with adjustable height
  • Carbon filter cartridges are provided.
  • Air stones are provided.
  • Setup is simple.
  • Designed for use with gravel


  • There is no air pump or airline tubing provided.
  • Plate clamps made of plastic are prone to breaking.


Undergravel Filter Imagitarium

The Imagitarium Undergravel Filter is the greatest undergravel aquarium filter for the money. This filtration system comes in 10-gallon and 29-gallon versions and may be used in both freshwater and saltwater tanks, however it is not reef safe.

This filter kit comes with two snap-together plates, however the plates do not need to be snapped together for the filter to function properly because the plates may function side by side without being linked. Lift tubes, air stones, and interchangeable carbon filter cartridges are all included in this set.

This undergravel filter is incredibly cost-effective and takes filter cartridges from different manufacturers, making replacement cartridges much easier to obtain when required. This filtering system lacks airline tubing and an air pump.


  • The best value for money
  • Saltwater or freshwater
  • Plates can work in tandem.
  • Included are lift tubes and air stones.
  • Carbon filter cartridges are provided.
  • Accepts filter cartridges from different manufacturers


  • There is no air pump or airline tubing provided.
  • Plates may be tough to connect.
  • There are just two sizes available.


Lee’s Premium 40 55 Undergravel

Lee’s 40/55 Premium Undergravel Filter, or any of the Lee’s undergravel filters, is the best premium undergravel filter. These filters are available in six capacities ranging from 10 to 125 gallons. This filtering system is suitable for both freshwater and saltwater.

Lee’s Premium Undergravel Filters are unusual in that they are composed of a single high-quality plastic plate that is designed to withstand the weight of an aquarium substrate. The installation is simple, and having only one plate eliminates one step from the procedure.

This kit also contains two non-adjustable lift tubes, air stones, and interchangeable carbon filter cartridges. For those who choose not to use them, these cartridges cannot be completely removed from the filtering system.

This system accepts components from various brands and, as an added plus, it is black, which allows it to blend into more substrates than white or blue undergravel filters. The airline tube and air pump are not included.


  • One crack-resistant plastic plate
  • There are six sizes available, ranging from 25 to 125 gallons.
  • Both freshwater and saltwater are safe.
  • Included are lift tubes and air stones.
  • Carbon filter cartridges are provided.
  • Accepts components from other manufacturers
  • The color black merges easily.


  • There is no air pump or airline tubing provided.
  • Premium cost
  • The lift tubes are not adjustable.
  • Cannot work properly until the carbon filters are installed.


Bottom Undergravel Filteration

The Aquarium Equip Undergravel Filteration Kit is not your typical undergravel filter. This is made up of a series of tubes and elbows that sit beneath the substrate and allow water to flow through.

This filtering system is offered in two sizes: 10-gallon and 55-gallon. It is suitable for use in freshwater, saltwater, and on coral reefs.

This sort of undergravel filtration system can be used in conjunction with air pumps or directly linked to other filtration systems such as canister filters.

It is not intended to be the sole filter in an aquarium. This kit simply includes the plastic tubes and elbows; no air stone, air pump, or other equipment is included.

The Aquarium Equip Undergravel Filteration system, unlike other undergravel filters, may be utilized with sand substrate. It should ideally be used in conjunction with a bigger substrate, such as gravel, to increase water movement.


  • Safe for freshwater, saltwater, and reef environments.
  • Design that is one of a kind
  • Can be utilized to enhance the present filtering system.
  • It is suitable for usage with sand.
  • Includes all of the plastic tubes, elbows, and joints required to make a lift tube.
  • The color black merges easily.


  • It is not possible to rely solely on filtration.
  • There is no air pump, stone, or airline tubing included.
  • There are just two sizes available.
  • There is no place to store any form of filter cartridge or material.


ISTA Aquarium Equipment Undergravel

The Aquarium Equip ISTA Undergravel Filter is inexpensive, but only comes in one size, which is suitable for small tanks up to 10 gallons. This undergravel filter is suitable for both freshwater and saltwater aquariums.

This device differs from other undergravel filters in that it does not rest flat on the tank’s bottom.

Instead, the plate is linked to small legs that lift it off the ground, but there are no sides to keep waste and substrate from getting below the plate, which can lead to waste accumulation.

The plate may be cut to fit unusual shaped tanks and still work as long as the lift tube can be connected. A plastic air “stone” and an adjustable height raise tube are also included in the kit. This filter works well with gravel.

This undergravel filter is compatible with air pumps as well as other filtration systems such as canister filters and HOB filters. This filter will not perform properly as the only filter in the tank since it lacks carbon filters.


  • Both freshwater and saltwater are safe.
  • Plate may be sliced into unusual shapes and sizes.
  • Cost-effective
  • The lift tube may be adjusted.
  • Can be utilized to enhance the present filtering system.


  • Size is small.
  • Waste may accumulate behind the elevated plate.
  • The air stone is composed of plastic.
  • It is not possible to rely solely on filtration.
  • There are no carbon filter cartridges.


Undergravel uxcell Plastic Fish Tank

The uxcell Plastic Fish Tank Undergravel Filter is a low-cost option for tanks of various sizes. This kit includes 24 little plates that may be joined together to produce a bigger plate. They can be arranged side by side or end to end.

This set contains 24 black plastic plates, a lift tube, and an air hose line connected to an air stone. It lacks an air pump and full-length airline tube. While the plates are black, the lift tube joints are white, which is visible in an aquarium.

This system can be linked to an existing filtration system, such as a HOB or a canister, but it should not be utilized as the primary source of filtration. There is no carbon filtering or other chemical filtration.


  • Sized to work with snap-together plates
  • Can be utilized to enhance the present filtering system.
  • The color black merges easily.
  • Cost-effective


  • It is not possible to rely solely on filtration.
  • There are no carbon filter cartridges.
  • Lift tube joints are white.
  • There is only one lift tube and one air stone provided.
  • There is no air pump or complete airline tubing provided.
  • Plates cannot be cut to fit irregular forms.


These evaluations cover a variety of the best undergravel aquarium filters, providing you with alternatives for what would work best in your tank. The Penn Plax Premium Under Gravel Filter System was BestForPets‘ (bestforpet.org) choice for the best overall product because to its outstanding quality and performance, but for the greatest value, the Imagitarium Undergravel Filter has a comparable appearance and function. Lee’s 40/55 Premium Undergravel Filter is a high-end product. This product has a basic, clean design built of high-quality materials


Are Undergravel Filters Effective?

Yes, they are quite useful if you have a tank with gravel, sand, or another substrate. However, they are only as good as your entire setup. The undergravel option will disappoint you if you do not have a powerful enough complete filter operation.

Are Undergravel Filters Extinct?

Many people fail to utilize an undergravel filter because they are unaware that they require one. They are, however, far from obsolete, and are vital when gravel or rocks are present. There are methods to avoid utilizing them, yet they do serve a function.

Furthermore, they are still widely available on the market and are reasonably priced. They are widely available and are not going away anytime soon. There is a common misperception that they are outdated.

Is an Undergravel Filter Necessary for My Aquarium?

We strongly advise utilizing an undergravel filter if you have gravel in a tank with fish. It is the only method to keep ammonia and fish waste at bay in order to create a genuinely safe environment not just for the fish but also for the plants.

What is the best type of aquarium filter?

It all depends on what’s in your tank. Most people will tell you that biological filtration is the best option, however it is not always the best option. You may need to conduct some study based on the contents of your aquarium to determine the sort of filtration you require.

Buyer's Guide


Your catch

The sort of fish you have will assist you choose an undergravel filter, assuming you choose one at all! Loaches and cichlids, which prefer to burrow or dig, are not good choices for undergravel filters.

Undergravel filters must be buried at all times in order to function securely and properly. In a tank with a lot of landscaping fish, your filter may become regularly exposed, reducing its efficiency.

The Bioload in Your Tank

Not only do the sorts of fish you have matter, but so do the number of fish you have and the size of those fish! A 40-gallon tank with 10 neon tetras will have a far lower bioload than a 40-gallon tank containing 5 goldfish.

Undergravel filters are not suitable for high bioload tanks, but they are ideal for understocked, suitably stocked, or low bioload tanks containing tiny fish or invertebrates.

Size of your tank

Undergravel filters work best in tanks less than 55 gallons, although they may also be utilized in bigger tanks. Just make sure you obtain the proper size undergravel filter for your tank, or if you have a larger tank, get more than one!

It won’t harm to have more than one undergravel filter in your tank if you have the outlet space. More filtering is nearly always preferable to less. You’ll only have to make sure you clean and maintain both filters on a regular basis to avoid promoting the growth of undesirable germs.

Your Supporting Material

Most undergravel filters operate best with gravel or pebbles as the substrate. Sand is frequently too fine and will fill up the area beneath the plate, reducing the filter’s capacity to draw water down through the substrate and colonize microorganisms.

If your substrate is too huge, such as river boulders, an undergravel filter will be ineffective as well. When it comes to undergravel filters, a substrate that is large enough to not go under the filter plate but tiny enough to have a high surface area will offer you the most bang for your money.

Plants you have

If your tank is thickly planted with plants in the substrate, an undergravel filter will most likely cause your plants to become stunted or die. An undergravel filter will obstruct root growth, and installing one may disrupt your plants.

Furthermore, if you have plants that do not like to be moved once planted, such as crypts, putting an undergravel filter after you’ve established your planted tank can stress and perhaps kill your plants.

If your tank is filled of floating plants or Java ferns stuck to driftwood, an undergravel filter will not harm your plants.

Your Filtration System

Because undergravel filters are a sort of filter, this one is a little problematic. These filters, however, are not especially effective on their own. All undergravel filters will operate best in conjunction with another sort of filtration, but the type of filtration you employ is entirely up to you.

Most undergravel filters may be linked to another filtering system, so increasing the efficacy of the other system. They may be linked to almost any type of filtration system, but they perform best when combined with a HOB, powerhead, or canister filter.

If your tank filtration consists of an undergravel filter and a sponge filter, you will most likely not have the water circulation and waste collection that your tank requires.

What Else Will You Need to Set Up an Undergravel Filter


Undergravel filters require 2.5-3 inches of substrate to function properly. In general, 1 pound of substrate per gallon will provide you 1-2 inches of depth, depending on the size of your tank’s floor space.

This implies that when you go to buy your substrate, you may need to obtain 1.5-2 pounds per gallon. It will also be much simpler on you if you install an undergravel filter at the same time as you install the substrate. Otherwise, you’ll have to dig through the substrate to install the undergravel filter.

Air compressor

The air stone in the undergravel filtration system will be powered by an air pump. It’s critical to acquire an air pump that’s the right size for the tank you have; otherwise, you’ll likely wind up with a weak bubbler instead of a functional filtration system.

Tubing for airplanes

The airline tube that links everything is the heart and soul of any air pump, however most pumps do not have it.

Read the air pump’s description or box carefully to determine if it comes with tubing and, if so, if it’s long enough for your needs. Airline tubing is often cheap and readily available.

Other types of filtration

If your tank is already established, ensure sure you have another sort of filtration in place. If your tank is new and cycling with no fish, you can add an undergravel filter and a second filter of a different type later.

Remember that an undergravel filter will not create the same water currents as a HOB or canister filter, so using one alone, especially in a bigger tank, may result in poor water conditions.

Author Image

Dr. Deborah Fletcher

Deborah R. Fletcher, DVM, is a skilled veterinarian with more than 15 years of experience dealing with companion and exotic animals. She has experience caring for a variety of animals, including household cats and dogs, reptiles, birds of prey, and even primates. Dr. Fletcher is a valuable part of the BestForPets team, where she contributes to their aim of providing pets and their owners with the finest possible treatment and services.

Veterinarian (DVM) Dr. Deborah Fletcher


Rated 0 out of 5
0 out of 5 stars (based on 0 reviews)
Very good0%

There are no reviews yet. Be the first one to write one.

Related articles