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Top 9June 2025

Best Under Gravel Aquarium Filter 20 Gallon

We made a list of the top 9 Under Gravel Aquarium Filter 20 Gallon based on verified reviews, popularity and other factors which we summarized for you in this list.

Best Choice

Penn-Plax Replacement Media (2 Pack) – Fits Multi-Pore and Undergravel “E” Filters – Provides Chemical Filtration (FC2)

Penn-Plax Replacement Media (2 Pack) – Fits Multi-Pore and Undergravel “E” Filters – Provides Chemical Filtration (FC2)

✓REPLACEMENT FILTER MEDIA: These Cartridges are made to fit the lift tubes of Muti-Pore and Undergravel “E” filters, serving as a replacement for when it’s time to cycle out aquarium filter media. We recommend replacing them once a month.
✓TOP-QUALITY CARTRIDGE: Cartridges come together in a 2 Pack. For best results, replace cartridges every 2 to 4 weeks. They’re lightweight, disposable, and are safe for Freshwater and Saltwater aquariums.
✓CHEMICAL FILTRATION: In addition to absorbing ammonia, nitrites, nitrates, and phosphates in a timely manner, these Cartridges also remove harmful chemicals and toxins, clear up discolorations, and reduce foul odors from your tank.
✓OLD SCHOOL: There has been a burst of growth, development, and ingenuity within the aquatic industry, and although we are a part of this as well, we still provide replacement media for undergravel aquarium setups.
✓SHOP PENN-PLAX FOR ALL YOUR PET’S NEEDS: Penn-Plax is a manufacturer and distributor of top quality pet supplies, who specialize in creating excellent pet products for animals, both great and small.

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Penn-Plax Undergravel Aquarium Filter for 15-20 (high) Gallon Tanks – Two 11.2” x 11.25” Plates – Under Gravel System for Clear, Clean Water – Safe for Freshwater and Saltwater Tanks

Penn-Plax Undergravel Aquarium Filter for 15-20 (high) Gallon Tanks – Two 11.2” x 11.25” Plates – Under Gravel System for Clear, Clean Water – Safe for Freshwater and Saltwater Tanks

✓NOTHING LIKE OLD SCHOOL: The Clear-Free Premium Under Gravel Filter is air driven and utilizes an Air Pump (not included) to cycle crystal clear water throughout your aquarium, while keeping a crisp and neat look inside. This means there’s less “moving parts,” making for simplistic and easy maintenance. This filter is suitable for most 15 – 20 (high) gallon aquariums.
✓BIOLOGICAL, CHEMICAL, AND PHYSICAL FILTRATION: As air is pushed through the Air Stones and rises through the Lift Tubes, water is gently suctioned through gravel and the filter plates, allowing both air and water to pass through the Filt-a-Carb Activated Carbon Cartridges. When water continues to be drawn through, anaerobic bacteria collects and colonizes within the gravel and filter plates.
✓ALSO AERATES YOUR TANK: Since the Clear-Free Premium Under Gravel Filter is air driven through the use of Air Stones and an Air Pump (not included), it also aerates your tank. In essence, your aquarium is being filtered and aerated at the same time, though the same system! It’s a filter and bubbler in 1!
✓ITEMS INCLUDED: The Clear-Free Premium Under Gravel Filter includes 2 Filter Plates, 2 Adjustable Lift Tubes, 2 Straight Airline Tubes, 3 Filter Plate Connecters, and 2 Replaceable Filt-a-Carb Activated Carbon Media Cartridges.
✓MEASUREMENTS: Each Filter Plate Separately = 11.25” (W) x 11.2” (D) / Filter Plates Together = 22.5” (W) x 11.2” (D) / Each Lift Tube at Filter Plate Base = 12” – 15”
✓COLOR MAY VARY: Please note: the plates that go on the bottom of your tank beneath a layer of gravel or other substrates may be Blue or Black.

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8% Discount

Penn-Plax Undergravel Aquarium Filter for 20 (Long) - 29 Gallon Tanks – Two 14” x 11.1” Plates – Under Gravel System for Clear, Clean Water – Safe for Freshwater and Saltwater Tanks

Penn-Plax Undergravel Aquarium Filter for 20 (Long) - 29 Gallon Tanks – Two 14” x 11.1” Plates – Under Gravel System for Clear, Clean Water – Safe for Freshwater and Saltwater Tanks

✓NOTHING LIKE OLD SCHOOL: The Clear-Free Premium Under Gravel Filter is air driven and utilizes an Air Pump (not included) to cycle crystal clear water throughout your aquarium, while keeping a crisp and neat look inside. This means there’s less “moving parts,” making for simplistic and easy maintenance. This filter is suitable for most 20 (long) – 29 gallon aquariums.
✓BIOLOGICAL, CHEMICAL, AND PHYSICAL FILTRATION: As air is pushed through the Air Stones and rises through the Lift Tubes, water is gently suctioned through gravel and the filter plates, allowing both air and water to pass through the Filt-a-Carb Activated Carbon Cartridges. When water continues to be drawn through, anaerobic bacteria collects and colonizes within the gravel and filter plates.
✓ALSO AERATES YOUR TANK: Since the Clear-Free Premium Under Gravel Filter is air driven through the use of Air Stones and an Air Pump (not included), it also aerates your tank. In essence, your aquarium is being filtered and aerated at the same time, though the same system. It’s a filter and bubbler in 1.
✓ITEMS INCLUDED: The Clear-Free Premium Under Gravel Filter includes 2 Filter Plates, 2 Adjustable Lift Tubes, 2 Straight Airline Tubes, 3 Filter Plate Connecters, and 2 Replaceable Filt-a-Carb Activated Carbon Media Cartridges.
✓MEASUREMENTS: Each Filter Plate Separately = 14” (W) x 11.1” (D) / Filter Plates Together = 28” (W) x 11.1” (D) / Each Lift Tube at Filter Plate Base = 13” – 16”

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Penn-Plax Undergravel Aquarium Filter for 40-55 Gallon Tanks – Four 11.25” x 11.25” Plates – Under Gravel System for Clear, Clean Water – Safe for Freshwater and Saltwater Tanks (CFU55)

Penn-Plax Undergravel Aquarium Filter for 40-55 Gallon Tanks – Four 11.25” x 11.25” Plates – Under Gravel System for Clear, Clean Water – Safe for Freshwater and Saltwater Tanks (CFU55)

✓NOTHING LIKE OLD SCHOOL: The Clear-Free Premium Under Gravel Filter is air driven and utilizes an Air Pump (not included) to cycle crystal clear water throughout your aquarium, while keeping a crisp and neat look inside. This means there’s less “moving parts,” making for simplistic and easy maintenance. This filter is suitable for most 40 – 55 gallon aquariums.
✓BIOLOGICAL, CHEMICAL, AND PHYSICAL FILTRATION: As air is pushed through the Air Stones and rises through the Lift Tubes, water is gently suctioned through gravel and the filter plates, allowing both air and water to pass through the Filt-a-Carb Activated Carbon Cartridges. When water continues to be drawn through, anaerobic bacteria collects and colonizes within the gravel and filter plates.
✓ALSO AERATES YOUR TANK: Since the Clear-Free Premium Under Gravel Filter is air driven through the use of Air Stones and an Air Pump (not included), it also aerates your tank. In essence, your aquarium is being filtered and aerated at the same time, though the same system. It’s a filter and bubbler in 1.
✓ITEMS INCLUDED: The Clear-Free Premium Under Gravel Filter includes 4 Filter Plates, 4 Adjustable Lift Tubes, 4 Straight Airline Tubes, 9 Filter Plate Connecters, and 4 Replaceable Filt-a-Carb Activated Carbon Media Cartridges.
✓MEASUREMENTS: Each Filter Plate Separately = 11.25” (W) x 11.25” (D) / Filter Plates Together = 45” (W) x 11.25” (D) / Each Lift Tube at Filter Plate Base = 13.25” – 16.5”

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23% Discount

Pawfly Aquarium Corner Sponge Filter Quiet Small Fish Bio Foam Filter with Natural Stones Gravels and Ceramic Rings for Betta Fry Shrimp Fish Tanks up to 50 Gallons (Air Pump Not Included)

Pawfly Aquarium Corner Sponge Filter Quiet Small Fish Bio Foam Filter with Natural Stones Gravels and Ceramic Rings for Betta Fry Shrimp Fish Tanks up to 50 Gallons (Air Pump Not Included)

✓Multi-layer Fine Sponge: Provide mechanical and biological filtration and trap debris or wastes without sucking up your fish. Keep fish tanks crystal clear and healthy.
✓Further Cleaning: The gravels inside absorb excess damaging substances and release trace elements. And the ceramic rings can cultivate beneficial substances. Always keep water fresh.
✓For 50 Gal Tanks: Measure 3.1" R x 6" H. Fit for 20-50 gallon fish tanks. You can change the sponge sequence at will and customize the filter materials according to the breeding density of the fish.
✓Quiet Aeration: Air powered and cause no disturbance to your daily life. The wide duck-billed air outlet port brings more bubbles to promote oxygen circulation.
✓Easy to Clean: The filter can be easily detached for cleaning. Rinse the sponges every 2 to 4 weeks with aquarium water ONLY. Avoid soaking or washing them in tap water! Replace the white sponge every 2-3 months!

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CORISRX BEST OF YOUR LIFESTYLE Undergravel Filter 11.8" X 5.9" Fish Tank Under Gravel Filter

CORISRX BEST OF YOUR LIFESTYLE Undergravel Filter 11.8" X 5.9" Fish Tank Under Gravel Filter

✓Circulate the water under gravel layer in order to reduce the corruption of gravel.
✓The gravel bed provides tremendous surface area for Nitrobacteria and keeps your water crystal clear.
✓The filter plate can be connected with air pump, filter pump, submersible power head and hang-on filter to increase the circulation and help with mechanical and chemical filtration.
✓Adjustable lift tube can be modified at your desire height. Silence design tube head can reduce noise.
✓Air stones will not stock or collapse. Works freshwater and saltwater tanks

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TEHAUX Hexagon Aquarium Undergravel Tank 20pcs Convenient Fish Tank Bottom Plate PVC Splicing Clapboard Bottom Fish Tank Divider Aquarium Stand (Black)

TEHAUX Hexagon Aquarium Undergravel Tank 20pcs Convenient Fish Tank Bottom Plate PVC Splicing Clapboard Bottom Fish Tank Divider Aquarium Stand (Black)

✓Under Gravel Aquarium Hole Design: The fish tank gravel plate is ideal for breeding large dragon fish and sea fish, enhancing the overall aquarium environment
✓Convenient and Practical: The undergravel filter plate is easy to install with a receiving type butt installation and can be cut to fit your specific needs
✓Bottom Filter Material Partition: The plastic mesh panels allow for the separation of filter materials, enabling the combination of different types of media to optimize water flow and stability
✓What You Get: The package includes 20 black grid dividers, each measuring 5.9x5.9x1.06 inches, perfect for gravel filtration in your fish tank
✓Durable Pvc Material: Made from pvc, these undergravel filter plates are slightly submerged and offer good toughness, ensuring long-lasting use in your aquarium

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coospider-repta 200GPH Aquarium Filter, U-V for Aquarium for 20-75 Gal Tank, Submersible Pump Filter for Green Water and Algae Clean, Ultra-Silent Green Killing Machine with Fish Tank Deodorization

coospider-repta 200GPH Aquarium Filter, U-V for Aquarium for 20-75 Gal Tank, Submersible Pump Filter for Green Water and Algae Clean, Ultra-Silent Green Killing Machine with Fish Tank Deodorization

coospider-repta

✓4-IN-1 MACHINE - Aquarium Filter integrates four functions: Filtration, Deodorization, Oxygenation, and Water circulation. The flow rate of 200GPH, Power of 10W. Suitable for 20-75 Gallon fish tanks.
✓POWERFUL ALGAE-KILLING EFFECT - Aquarium U- Vutilizes double filtration with a U-V lamp and sponge filter. 10W disinfection lamp can improve green water within one day.
✓INDEPENDENT SWITCH CONTROL - The filter has independent switch. When you only want to use the aquarium filtering function, you can turn off the fish tank U-V light separately.
✓DOUBLE OXYGENATION CAPACITY - With two water outlets, you can adjust the water outlet method to increase the oxygenation and wave-making effect, promoting water circulation.
✓DEODORIZE - If the fish tank is full of algae, there will be an accompanying odor. This green killer machine can effectively reduce unpleasant odors in your fish tank.

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XMHF Aquarium Fish Tank Bottom Under Gravel Filter Board Plate Plastic 24-Pcs

XMHF Aquarium Fish Tank Bottom Under Gravel Filter Board Plate Plastic 24-Pcs

✓Product Name: Aquarium Under Gravel Filter 24 Pieces
✓Material : Plastic;Each Size : 140 x 70 x 12mm/5.5" x 2.8" x 0.5"(L*W*T)
✓Tube Size(Approx.) : 32 x 2.5cm/ 12.6" x 1"(H*D);Hose Hole Diameter : 5mm/0.2"
✓Air Stone Size : 2.5 x 1.4cm/1" x 0.6"(L*D);Main Color : Black, Clear
✓Weight : 474g; Package Content : 24 x Fish Tank Under Gravel Filter 1 x Tube 1 x Air Hose Line and Air Stone

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