An effective biological filter system is essential to provide a safe environment for your fish and other animals, regardless of the size of your tank or whether you have a freshwater or marine setup.

What is the reason for this? Well, any living organism produces waste, and this waste, along with uneaten food, dead plant matter, and other factors, sets off the Nitrogen Cycle in your aquarium. The water in your tank will easily become overloaded with ammonia, nitrite, and nitrates if you don’t have a biological filtration device, all of which will damage, if not destroy, your fish.

The undergravel filtration method is regarded as somewhat outdated among the different types of filter systems available today, and it is often overlooked in favor of more complicated technological systems. The UGF, on the other hand, is currently experiencing a revival in popularity.

A Quick View at the Top 5 Undergravel Filters

We’ll go over what makes Undergravel Filters so great, how they work, and how to keep one in good shape in this guide. We’ve also tracked down and tested five of the best undergravel filter systems on the market just for you.

Product Features

Penn Plax Premium Undergravel FilterPenn Plax Undergravel Filter

Capacity: 29-Gallons
Dimensions: 28 x 11 inches
Lee's 5 Original Undergravel Filter

Lee’s 5 Original Undergravel Filter

Capacity: 5.5-Gallons
Dimensions: 7.5 x 15 inches
Lee's 10 Premium Undergravel Filter

Lee’s 10 Premium Undergravel Filter

Capacity: 10-Gallons
Dimensions: 10 x 20 inches
Aquarium Equip ISTA Undergravel Filter

Aquarium Equip ISTA Undergravel Filter

Capacity: 10-Gallons
Dimensions: 5.9 x 11.8 inches
Penn Plax Premium Under Gravel Filter System

Penn Plax Premium Under Gravel Filter System

Capacity: 40 to 55-Gallons
Dimensions: 11.5 x 11.5 inches

There was a time when fish keepers only had a few filtering options: inexpensive undergravel filters, midrange HOBs, and costly canister systems. When I first started keeping fish, there were only two brands to choose from, and neither HOB offered tanks smaller than 10 gallons or larger than 100 gallons.

Undergravel Filters: An Overview

Undergravel filters (UGFs) were the most popular filtration device for most aquarists when I first started keeping fish 30 years ago, and they are still the most basic type of filter available today.

A UGF is a rectangular plastic grate or plate that you position underneath the substrate on the bottom of your aquarium. The filter system’s mechanical feature pulls water down through the substrate and over the plate, creating a large surface area for waste-consuming bacteria to colonize. That is why the UGF is the perfect option for a highly effective biological filter for your aquarium.

Basic UGFs operated by a simple air pump are ideally suited for aquariums with a capacity of fewer than 55 gallons, but they can be used in larger aquariums with the addition of a powerhead.

When compared to canister filters, box filters, and most HOB systems, undergravel filter systems are usually the cheapest choice.

How An Undergravel Filter Works

Undergravel filter cicle

An undergravel filter is made up of one or more plastic plates that are pierced with small holes or slots and are flat or slightly graded. You place the filter plate on the tank’s bottom and cover it with the substrate of your choice. The best substrate to use is gravel or coarse sand, as fine media tends to cover the holes and obstruct water circulation through the plate and through the substrate.

Two vertical “uplift” tubes are inserted into circular slots in the filter plate’s back corners, with the tops of the tubes below the water’s surface. Air stones are fixed to the lengths of the airline within each of the uplift tubes. A pump or powerhead at the top of each tube draws water and bubbles formed by the air stones up through the tube.

As a result of the suction action, water is drawn down through the substrate and into the filter plate, providing dissolved oxygen to the beneficial bacteria colonies. The end result is a stable, well-oxygenated atmosphere for your fish, as well as a thriving mass of bacteria and an effective biological filter system.

Undergravel Fish Tank Filters Have Many Advantages.

Penn Plax Premium Under Gravel Filter System

There are many advantages of using undergravel filters.

It’s reliable and easy to use.

The UGF is remarkably simple compared to some of the more complex and sophisticated filters available, and with that simplicity comes reliability. That’s because there’s very little that can go wrong in a machine that doesn’t have any moving parts.

An air pump or a powerhead is the mechanical component of the UGF, and if you choose a reliable one, the device should work flawlessly.

Running in silence.

A UGF device is totally quiet, apart from the gentle hum of the pump and the soothing sound of bubbling water, which is fantastic news if you want to keep your aquarium in a workroom or bedroom.

Maintenance Requirements are minimal.

There are no sticky sponge filters or cartridges to wash or replace with an undergravel filter. Simply vacuum the gravel once a week as part of a partial water upgrade, just like you would for any other filter device.

Biological Filtration of the highest quality.

A UGF utilizes the entire floor of your aquarium, unlike other filter systems that only include a few square inches of media on which bacteria can develop. So long as you keep the gravel clean and vacuum away solid waste particles, your water can stay super-clean, clear, and safe for your fish.


You’ll have a bulky, hideous box filter on display in your tank unless you have an external canister filter or sump concealed under your aquarium in the cabinet. For a UGF, this is not the case.

The filtering system The filter plates of the UGF device is concealed under the substrate, leaving only two clear plastic columns full of bubbles visible in your tank. Place tall plants in a position to block the uplift tubes if you don’t want to see them.

Operation Costs are Low.

Bottom gravel systems are inexpensive to buy and operate. That’s it! Once you’ve purchased the machine as well as the pump or powerhead, you’re done! You won’t have to buy costly filters or new filter media, and the machine won’t break until the pump fails.

Suitable For Bad Swimmers.

If you hold fish that can’t swim well, a standard filter system that can’t be changed may produce an excessively strong flow. Betta fish and fancy goldfish, for example, do not like a heavy water current, so a softly bubbling UGF is suitable for them.

Easily Customizable

Aquarium Equip ISTA Undergravel Filter

A filter system undergravel can be easily customized. You may, for example, select a heavy power supply instead of a small pump for a better water flow through the gravel.

You can also add a chemical filtration element, by buried under the gravel on top of the filter platter with a porous filter bag filled with carbon or zeolite.

By adding a sponge filter layer or floating onto the filter plates below the substratum, the biological filtration element can be overloaded. This innovation can also be applied in marine and brackish tanks.

The disadvantages of Using Undergravel Filters.

Solid waste particles floating in the water are drawn down into the gravel, slowing the flow of water and denying oxygen to the bacteria on the filter plate. As a result, the biological filtration component of the device becomes less effective over time, and the water quality deteriorates. As a result, many hobbyists opt for a secondary filter system that removes solid waste before it can clog the gravel.

Chemical Filtration

Chemical filtration is not present in most UGFs. Some, on the other hand, have an activated carbon cartridge or pouch that sits above each of the uplift tubes. The problem with this setup is that the cartridges only last longer than a few days until they need to be replaced. Placing a cartridge on top of the uplift tubes often helps to limit water flow through the filter system.

Choosing the proper Undergravel Filter

There are a few things you should remember before you decide on a UGF:

Aquarium dimensions.

Some undergravel filters are built of a single platform, while others are built of two or more plates. Before choosing a UGF, measure your aquarium floor and check the product packing dimensions to ensure that the tank that you select suits your tank or, if possible, can be cut to scale.

Additional Items

UGFs do not usually come with one included in the kit, unlike other filter systems with an integrated power supply and pump. So a pump or a powerhead must be purchased. Generally, larger aquariums over 55 gallons need an electricity supply to produce enough suction to make the UGF functional.

In general, the flow rate from the pump is at least 60 GPH when the filter plate is placed underneath three inches of gravel (gallons per hour).

Form of Filtration.

If you keep really dirty fish, such as goldfish, UGFs can not be the best option for you. Nonetheless, I was able to successfully use a UGF with a 30-gallon setup that housed fancy goldfish, despite vacuuming the gravel every week and using a huge pump.

If you want to operate a device with chemical filtration, you’ll need to add activated carbon filters to the UGF system, as previously mentioned.

Maintenance of the Undergravel Filter

The biggest disadvantage of using a UGF method is that solid waste particles collect between the gravel fragments that make up the substrate. Over time, the blockage prevents water from passing through the bacteria in the substrate and down through the filter plates, depriving the bacteria of oxygen and resulting in foul water pockets.

That shouldn’t be a concern if you’re careful about performing partial water changes every week and agitating and vacuuming the substrate to eliminate general detritus and fish waste.

It’s also a good idea to take the tank fully out every 18 months or so to clean the tank bottom, remove and rinse the filter plates, and swill the gravel via aquarium water to remove any accumulated muck.

Algae can expand both inside and outside the uplift columns at times. You’ll need to clean the tubes with a soft-bristled bottle brush as needed.

Best Under Gravel Filters Reviews.

We’ve chosen five of the best UGFs currently on the market and reviewed them for you in this section of our guide.

1.Penn Plax Undergravel Filter.

Penn Plax Premium Undergravel Filter

Capacity: 29-Gallons
Dimensions: 28 x 11 inches

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The UGF can be used in both marine and freshwater aquariums. The filter plates are designed to be used with a gravel substrate and are ideal for use in a standard size tank of 28” x 19”.

The system includes two slatted filter plates that go under the gravel at the bottom of the tank. Two uplift tubes are supplied with air stones and extensions and attach to the filter plates. Two activated carbon filter cartridges are also included.

You’ll need to purchase an air pump or powerhead separately, as with most UGF systems.

Penn Plax Premium Undergravel Filter Pros & Cons
  • Low-cost
  • There is very little upkeep needed.
  • Role of chemical filtration
  • There is no air pump included.

2. Lee’s 5 Original Undergravel Filter.

Lee's 5 Original Undergravel Filter

Capacity: 5.5-Gallons
Dimensions: 7.5 x 15 inches

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Lee’s Original UGF comes in a variety of sizes, so you’ll be able to find one that suits your tank.

There is only one filter plate in the device, which is made of solid, durable plastic. If you want to use a powerhead for your system, there is a flow-through setup included. Because of the super-strong material, the filter plate would not degrade in a marine or brackish tank.

Water circulates well through the substrate and filter plate thanks to the use of two customizable uplift columns. In addition, the package includes airline tubing and air stones. However, as with most UGFs, a pump or powerhead must be purchased separately.

Lee’s 5 Original Undergravel Filter Pros & Cons
  • It’s easy to set up.
  • Uplift columns that can be adjusted.
  • Construction that is sturdy.
  • There is no air pump included.

3. Lee’s 10 Premium Undergravel Filter.

Lee's 10 Premium Undergravel Filter

Capacity: 10-Gallons
Dimensions: 10 x 20 inches

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Since Lee’s Premium UGF is a one-piece model, you must choose the appropriate size for your tank or purchase several units if you have a large aquarium. However, because of the larger plate size, you won’t need as many filter plates for a large tank as you would with other brands, making this a cost-effective option.

The filter plates are made of rugged and durable materials, allowing you to use the device in both marine and brackish tanks, as well as freshwater setups. The wide undergravel plates cycle the aquarium reasonably easily, unlike several canister or box filters, so you can get up and running faster.

Lee’s 10 Premium Undergravel Filter Pros & Cons
  • Simple to assemble
  • Robust construction
  • Maintenance criteria are minimal.
  • Air pump not included.

4. Aquarium Equip ISTA Undergravel Filter.

Aquarium Equip ISTA Undergravel Filter

Capacity: 10-Gallons
Dimensions: 5.9 x 11.8 inches

Check Price

This system can be used in conjunction with a normal air pump, HOB filter system, or powerhead to improve circulation and provide chemical filtration if desired. The uplift tubes can be trimmed to suit your aquarium perfectly, and the tube heads are cleverly built to minimize noise.

This undergravel device can be used in freshwater, marine, or brackish tanks, and the filter plate can be cut to match. The air stones supplied are of good quality and will not degrade or fall.

Aquarium Equip ISTA Undergravel Filter Pros & Cons
  • It is possible to trim it to fit.
  • Construction that is sturdy.
  • It can be used in both freshwater and saltwater aquariums.
  • No pump or powerhead included

5. Penn Plax Premium Under Gravel Filter System.

Penn Plax Premium Under Gravel Filter System

Capacity: 40 to 55-Gallons
Dimensions: 11.5 x 1.5 inches

Check Price

The Penn Plax UGF is one of the most common undergravel systems available for purchase.

The filter is designed for 40 and 50-gallon aquariums and is made up of four individual filter plates that clip together. You also get two extra-large uplift columns, generous airline lengths, and air stones. You also get two carbon filter cartridges, which keep the water crystal clear and free of the nasty, sulfurous odor that often afflicts UGFs.

This UGF can be used in both marine and freshwater aquariums, the materials used are durable and long-lasting, and the device is simple to set up and maintain. Take note that the filter plate connectors are very fragile and can easily break, so use caution while handling them and assembling the device.

Penn Plax Premium Under Gravel Filter System Pros & Cons
  • Easy Installation.
  • Useful in both freshwater and saltwater tanks..
  • The connectors for the filter plate are flimsy.

Final Thoughts.

I hope you found this guide to selecting the best undergravel filter device for your aquarium useful.

The Penn Plax Premium UGF kit is our favorite. At the time of writing, this is the most common undergravel filter on the market, and it is ideal for those with larger tanks of 40 to 50 gallons. The filter plates come in four separate units that clip together for a custom fit. The uplift columns are extra-large to allow for more water flow, and the device includes two activated carbon filter cartridges.

If you have a smaller tank, you can go for Lee’s Original Undergravel Filter, which comes in a variety of sizes, is very well-made, and can be used in both freshwater and saltwater.

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