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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)

4.3 4.3 out of 5 stars 3,536 ratings

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Aquarium Filter

Purchase options and add-ons

  • 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”

Customer ratings by feature

Easy to use
4.2 4.2
Easy to install
4.1 4.1
Value for money
4.1 4.1
Easy to assemble
4.0 4.0

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From the manufacturer

Penn-Plax Fish Pet Supplies Tank Aquarium Accessories Animal House Home Family Fun Kid Friendly Sand
CFU55 CFU 55 Penn-Plax Penn Plax Undergravel Under Gravel Filter Gallons Fish Tank Aquarium Wet

Suitable for 40 - 55 Gallon Tanks

Penn-Plax Pen Penn Plax PennPlax PenPlax Pet Accessories Supplies Dog Doge Puppy Pup Company Family
PENN-PLAX, manufacturer & distributor of top Pet Supplies.

PENN-PLAX is a family owned business that was established in 1956 in Brooklyn, New York. Over the years our goal remains the same: to enhance the pet ownership experience.

We specialize in creating excellent pet supplies for animals, both great and small. We're best known for producing pet products at affordable prices. Our brand, PENN-PLAX, is synonymous with innovation and quality, keeping your pet foremost in mind.

Clear-Free Premium Under Gravel Aquarium Filter

Powerful & Efficient Filtration

PENN-PLAX presents the Clear-Free Premium Under Gravel Aquarium Filter.

Those who’ve been around the aquatic block for a while know that Under Gravel Filters (UGFs) are a testament of time.

This 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.

It’s suitable for most 40 – 55 gallon aquariums.

CFU Under Gravel Undergravel Substrate Filter Fish Tank Aquarium Air Pump Bubble Carbon Cartridges

Take a Closer Look at the Clear-Free Premium Under Gravel Aquarium Filter

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!

Assembly Instructions:

  • To assemble your new filter, simply attach the plates together, assemble the lift tubes, attach the lift tubes to the filter plates, and then add the whole filter to your aquarium. Next, connect each lift tube to an air pump to power the filter. - Air Pump Not Included.

CFU10 CFU 10 Ten Undergravel Under Gravel Aquarium Fish Tank Filter Penn Plax Penn-Plax Hobby Clean CFU20 CFU 20 Twenty Undergravel Under Gravel UGF Filter Fish Tank Aquarium Filtration Bubble Bubbler CFU29 CFU 29 Twenty Nine Gallon Undergravel Under Gravel Filter Fish Tank Aquarium UGF Easy Penn CFU55 CFU 55 40 Gallon Aquarium Tank Undergravel Under Gravel UGF Fish Tank Aquarium Penn Plax Fishy
click here click here click here click here
Customer Reviews
4.3 out of 5 stars
1,548
4.4 out of 5 stars
1,204
4.4 out of 5 stars
1,258
4.3 out of 5 stars
3,536
Model Number CFU10 CFU20 CFU29 CFU55
Aquarium Size 10 Gallon 15 - 20 (high) Gallon 20 (long) - 29 Gallon 40 - 55 Gallon
Overall Measurements 19” (W) x 9.5” (D) 22.5” (W) x 11.2” (D) 28” (W) x 11.1” (D) 45” (W) x 11.25” (D)
Individual Plate Measurements 9.5” (W) x 9.5” (D) 11.25” (W) x 11.2” (D) 14” (W) x 11.1” (D) 11.25” (W) x 11.25” (D)
Number of Plates Included 2 2 2 4
FC2 Penn Plax Penn-Plax Replace Replacement Aquarium Filter Media Cartridge Activated Carbon Karbon FC3 Replacement Replace Aquarium Filter Media Cartridge Activated Carbon Karbon Penn-Plax Penn Plax AX2 Zeolite Zeo Lite Light Replace Replacement Filter Media Cartridge Aquarium Fish Tank Penn Plax AX3 Zeolite Zeo Lite Light Replace Replacement Filter Media Cartridge Aquarium Fish Tank Penn Plax
click here click here click here click here
Customer Reviews
4.6 out of 5 stars
1,625
4.6 out of 5 stars
1,625
4.6 out of 5 stars
130
4.5 out of 5 stars
55
Replacement Filter Media Type Filt-a-Carb Replacement Activated Carbon Media Cartridges Filt-a-Carb Replacement Activated Carbon Media Cartridges Ammonia-X Replacement Zeolite Media Cartridges Ammonia-X Replacement Zeolite Media Cartridges
Model Number FC2 FC3 AX2 AX3
Number of Cartridges 2 2 2 2

Product guides and documents

Product details

  • Is Discontinued By Manufacturer ‏ : ‎ No
  • Product Dimensions ‏ : ‎ 11.5 x 2.5 x 11.5 inches; 2.02 Pounds
  • Item model number ‏ : ‎ CFU55
  • Date First Available ‏ : ‎ July 6, 2010
  • Manufacturer ‏ : ‎ Penn Plax, INC.
  • ASIN ‏ : ‎ B003UTNOU6
  • Country of Origin ‏ : ‎ China
  • Customer Reviews:
    4.3 4.3 out of 5 stars 3,536 ratings

Looking for specific info?

Product Description

PENN-PLAX presents the Clear-Free Premium Under Gravel Aquarium Filter.
Those who’ve been around the aquatic block for a while
know that Under Gravel Filters (UGFs) are a testament of time.
This 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.
It’s suitable for most suitable for most 40 – 55 gallon aquariums, and is safe for Freshwater and Saltwater setups.

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
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”

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.

Important information

Directions

Wash with warm water before placing in aquarium.

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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)
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Price-19% $28.99
List:$35.99
-29% $44.99
List:$63.59
-28% $10.04
Typical:$13.85
-8% $48.99
List:$52.99
$14.99$11.45
Delivery
Get it as soon as Tuesday, Apr 2
Get it as soon as Tuesday, Apr 2
Get it as soon as Tuesday, Apr 2
Get it as soon as Tuesday, Apr 2
Get it as soon as Tuesday, Apr 2
Get it as soon as Tuesday, Apr 2
Customer Ratings
Value for money
4.1
3.2
4.1
4.6
4.0
Easy to use
4.2
4.0
4.8
3.9
Easy to assemble
4.0
4.2
4.2
4.0
Easy to install
4.1
4.5
4.3
Suction power
3.9
4.2
4.6
Sold By
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Amazon.com
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Amazon.com
Amazon.com

Customer reviews

4.3 out of 5 stars
4.3 out of 5
3,536 global ratings

Customers say

Customers like the performance, ease of assembly, and value of the pet supplies. For example, they mention that it works well, the instructions are easy to follow, and the price is great. They also like the filter, and appearance. That said, some complain about the quality, saying that the tubes are cracked and the plastic breaks easily. Opinions are mixed on cleanliness and fit.

AI-generated from the text of customer reviews

142 customers mention116 positive26 negative

Customers generally like the performance of the pet supplies. They say that it works well once configured, and is a good running system. Customers also mention that the sharp scissors work just fine.

"Good product" Read more

"...I say basic because these are so simple and easy to use and very effective.These are huge biological filters...." Read more

"...Good then and good now." Read more

"...Sharp scissor well work just fine. I have two sets kin my 125 gallon tank, make sure to keep the ends closed though...." Read more

73 customers mention56 positive17 negative

Customers find the pet supplies easy to assemble. They mention the instructions are easy to follow, and the product is simple and easy to use. Some say it's perfect to help with the entire setup.

"...It was pretty easy to set up. Once you kind of figure out how the first tube together it was easy set up...." Read more

"Wanted a planted tank. These are perfect to help with the entire setup. So far it's been a month and I've not had to change anything!..." Read more

"...The product was easy to assemble and came neatly packaged. This is not a seller issue...." Read more

"This is a GIANT pain to install and clean plastic tubes. The filter cartridges are expensive, and I don’t believe there is a way around it...." Read more

66 customers mention50 positive16 negative

Customers like the value of the pet supplies. They say it's a great product for the price, works excellent, and is a nice buy. Customers also mention that the materials and design are excellent for the value.

"I knew this item wasn't going to be anything special, it is a great price after all...." Read more

"Was a good price for a 55 gallon undergravel filter. Supports the gravel and rocks well and has not broken a panel. Seems to be well made...." Read more

"...work so we just have bubbles coming out of that one but it was okay for the price" Read more

"...The filter cartridges are expensive, and I don’t believe there is a way around it. If you are using on a small tank, it could work better for you...." Read more

30 customers mention26 positive4 negative

Customers like the filter. They say it's a great filter for aquariums, it filters the water well. Some customers also mention that it does a little more filtering than other filters. Overall, customers are satisfied with the quality and functionality of the filter, which makes it a good choice for setting up a biological filter for your aquarium.

"...This filter won't create waste for land fill, won't fail spectacularly, won't require you to keep the filter companies profits afloat, but it will..." Read more

"...These are huge biological filters...." Read more

"...Penn-Plax was the go-to 35 years ago, and still produces a quality under gravel filter. Good then and good now." Read more

"...they are more natural way to filter the water. it allows you to enhance it with other filter systems like canister or otb filter...." Read more

20 customers mention20 positive0 negative

Customers are satisfied with the appearance of the pet supplies. They mention that the underground plates are well designed with support stems strategically placed. They also say that it keeps the tank cleaner and more vibrant.

"...But it looks nice and my turtle does seem to enjoy it. So overall, it has its ups and downs." Read more

"...debris settles and collects under the panels well and keeps the tank cleaner looking." Read more

"It’s nice. It’s a pain in the butt to put together the directions don’t do it that well. I just watching a YouTube video...." Read more

"...These come with more than enough lift tubes. Great item to keep your tank looking great." Read more

38 customers mention25 positive13 negative

Customers are mixed about the cleanliness of the tank. Some mention that it does a great job keeping their tank clean, and the water is staying much cleaner. However, others say that it doesn't keep the tank clean and that it leaves a lot of debris at the bottom.

"...It does a really good job of keeping the sediment under the grate so it’s not on the rocks at all and doesn’t get stirred up by the fish...." Read more

"...Extra work to make it work, extra work to keep it clean, extra money spent...." Read more

"Makes cleaning easier" Read more

"...No gravel cleaning.Contrary to popular belief, they NEVER GET CLOGGED. EVER!Yes, you can have a planted aquarium...." Read more

32 customers mention18 positive14 negative

Customers are mixed about the fit of the filter. Some mention that it works great and is a perfect fit for their 55 gallon tank, while others say that it didn't fit their tank and the multiple plates together didn''t work well.

"The filter fit my tank perfectly...." Read more

"I bought this product for my 36 gallon bowfront naturally it doesn't fit well so a lot of cutting and rearranging is needed...." Read more

"...once assembled and placed, it blends into the tank wellit fits well in the tank, covering the whole bottom...." Read more

"...The second star was removed as the riser tubes are not as long as they should be or once were...." Read more

101 customers mention25 positive76 negative

Customers are dissatisfied with the quality of the pet supplies. They mention that the plastic breaks very easily, the tubes and filter heads are broken, and the ridged plastic is brittle. Some customers also say that the first order was damaged and the plastic is just become frail.

"...I repeatedly had issues with stuff building up in the tube I was able to get a brush and clean out a lot but not at the very bottom.. my tank is..." Read more

"...were made of a very ridged plastic, This was a bit brittle but posed no issues after they base was installed...." Read more

"Well made under gravel filter. I used it in a 40 Gallon tank I'm just starting to set up...." Read more

"I would have given 5 stars, but my first order was damaged, i.e., the heads and tubes were cracked. I sealed the cracks, so it is functional...." Read more

Let me explain the rating.
3 Stars
Let me explain the rating.
This item claims to be for a 40/55 gallon tank. Wrong. I’m not sure what 55 gallon tank these guys could possibly work in. But I have 7 inches of space that should have easily 5 inches of height left to fill. The tubes are not meant for a 55gallon tank. Refer to my picture’s. I’m not upset with the product but even the screens fell short of about 10 inches all the way across the front. The product was easy to assemble and came neatly packaged. This is not a seller issue. The seller sent and sold the item based off the manufacturer’s packaging using that as reference for the sale. If you have a 55 gallon tank. Measure it and go to a local pet store that specializes in selling aquatic products and get the right product for your tank.I will have to go and purchase extra tubes, measure, cut and connect them now to achieve the proper height. I will also have to not be reliant on the short screens and have to weekly clean the river rock that will lay directly on the glass.Extra work to make it work, extra work to keep it clean, extra money spent. Not happy with the purchase as there needs to be proper measurements for the plastic floor screens so other people aren’t having this issue. Other than that. The product will definitely do the job it was made to do. But not full scale for a 55 gallon tank.
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Ricardo
5.0 out of 5 stars Tal como lo necesitaba
Reviewed in Mexico on October 11, 2023
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John
5.0 out of 5 stars Good product
Reviewed in the United Kingdom on February 9, 2024
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NiNeufi
2.0 out of 5 stars Achtung: Filterkartuschen sollen alle 2 Wochen getauscht werden
Reviewed in Germany on June 21, 2023
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juancar
4.0 out of 5 stars Lo esperado
Reviewed in Spain on January 22, 2023
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Kyle
5.0 out of 5 stars Old tech, but it works !
Reviewed in Canada on January 11, 2021
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