Fluval Internal Filter U3
Ensure a healthy living environment for your beautiful swimmers in the tank with the Hagen Fluval U3 Underwater Filter. This multi-functional water filter features a complete 3-stage filtration process for maximum efficiency. To ensure excellent water quality and keepthe aquarium beautiful and fishes happy, the Fluval underwater filter has a newly designed media cartridge that traps more debris. Suitable for tanks up to 40gallon or 150L capacity, it can be used as a primary filter in a small tank or a supplement for larger setups.It ensures increased water movement and vital aeration. The 3-way filter system is adjustable. Its top output supports circulation and oxygenation. The integrated spray bar helps to maintain gentle and even flow while the bottom output ensures deepwater agitation. The Fluval U3 Filter has a slim and tall structure that looks equally fancy when placed horizontally or vertically inside the tank. The Fluval water filter can be used in all types of aquarium, whether it"s a shallow or sleek one. When the filters are exhausted, just flip the top lid and simply change the filter cartridge.Stage 1 of this 3-way filter removes particles. Stage 2 features the use of poly/carbon cartridge to trap debris to improve clarity and remove impurities. Stage 3 uses BIOMAX for biological filtration to create a healthy tank environment. The pack includes 2 foam pad cartridges, 2 poly/carbon sponge pad cartridges and Biomax nodes. All Fluval filters are made in Italy and are suitable for freshwater, saltwater and reptile environments.
Ensure a healthy living environment for your beautiful swimmers in the tank with the Hagen Fluval U3 Underwater Filter. This multi-functional water filter features a complete 3-stage filtration process for maximum efficiency. To ensure excellent water quality and keepthe aquarium beautiful and fishes happy, the Fluval underwater filter has a newly designed media cartridge that traps more debris. Suitable for tanks up to 40gallon or 150L capacity, it can be used as a primary filter in a small tank or a supplement for larger setups.It ensures increased water movement and vital aeration. The 3-way filter system is adjustable. Its top output supports circulation and oxygenation. The integrated spray bar helps to maintain gentle and even flow while the bottom output ensures deepwater agitation. The Fluval U3 Filter has a slim and tall structure that looks equally fancy when placed horizontally or vertically inside the tank. The Fluval water filter can be used in all types of aquarium, whether it"s a shallow or sleek one. When the filters are exhausted, just flip the top lid and simply change the filter cartridge.Stage 1 of this 3-way filter removes particles. Stage 2 features the use of poly/carbon cartridge to trap debris to improve clarity and remove impurities. Stage 3 uses BIOMAX for biological filtration to create a healthy tank environment. The pack includes 2 foam pad cartridges, 2 poly/carbon sponge pad cartridges and Biomax nodes. All Fluval filters are made in Italy and are suitable for freshwater, saltwater and reptile environments.
Ensure a healthy living environment for your beautiful swimmers in the tank with the Hagen Fluval U3 Underwater Filter. This multi-functional water filter features a complete 3-stage filtration process for maximum efficiency. To ensure excellent water quality and keepthe aquarium beautiful and fishes happy, the Fluval underwater filter has a newly designed media cartridge that traps more debris. Suitable for tanks up to 40gallon or 150L capacity, it can be used as a primary filter in a small tank or a supplement for larger setups.It ensures increased water movement and vital aeration. The 3-way filter system is adjustable. Its top output supports circulation and oxygenation. The integrated spray bar helps to maintain gentle and even flow while the bottom output ensures deepwater agitation. The Fluval U3 Filter has a slim and tall structure that looks equally fancy when placed horizontally or vertically inside the tank. The Fluval water filter can be used in all types of aquarium, whether it"s a shallow or sleek one. When the filters are exhausted, just flip the top lid and simply change the filter cartridge.Stage 1 of this 3-way filter removes particles. Stage 2 features the use of poly/carbon cartridge to trap debris to improve clarity and remove impurities. Stage 3 uses BIOMAX for biological filtration to create a healthy tank environment. The pack includes 2 foam pad cartridges, 2 poly/carbon sponge pad cartridges and Biomax nodes. All Fluval filters are made in Italy and are suitable for freshwater, saltwater and reptile environments.
Ensure a healthy living environment for your beautiful swimmers in the tank with the Hagen Fluval U3 Underwater Filter. This multi-functional water filter features a complete 3-stage filtration process for maximum efficiency. To ensure excellent water quality and keepthe aquarium beautiful and fishes happy, the Fluval underwater filter has a newly designed media cartridge that traps more debris. Suitable for tanks up to 40gallon or 150L capacity, it can be used as a primary filter in a small tank or a supplement for larger setups.It ensures increased water movement and vital aeration. The 3-way filter system is adjustable. Its top output supports circulation and oxygenation. The integrated spray bar helps to maintain gentle and even flow while the bottom output ensures deepwater agitation. The Fluval U3 Filter has a slim and tall structure that looks equally fancy when placed horizontally or vertically inside the tank. The Fluval water filter can be used in all types of aquarium, whether it"s a shallow or sleek one. When the filters are exhausted, just flip the top lid and simply change the filter cartridge.Stage 1 of this 3-way filter removes particles. Stage 2 features the use of poly/carbon cartridge to trap debris to improve clarity and remove impurities. Stage 3 uses BIOMAX for biological filtration to create a healthy tank environment. The pack includes 2 foam pad cartridges, 2 poly/carbon sponge pad cartridges and Biomax nodes. All Fluval filters are made in Italy and are suitable for freshwater, saltwater and reptile environments.
in 36 offers
The lowest price for Fluval Internal Filter U3 right now is $67.49 at Techinn.com, compared across 30 retailers.
The all-time low was $58.68 on 14 Feb 2026 — today's price is 15% above the lowest ever. That's a little above the best price we've seen.
Prices last updated 3 Aug 2026.
Last updated at 03/08/2026 06:00:51
Fluval U3 Underwater Filter 150l Clear
Delivery $29.99
Fluval U3 - Internal Filter
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Fluval U3 - Aquarium Internal Filter 600l/h Up To 150l Fish Tanks
Free delivery
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Fluval U3 Internal Fish Tank Aquarium Filter Design
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval U3 Internal Aquarium Water Filter 600l/h Fish Tank Filtration
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval Internal Filter U3
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval U Internal Filter - U3
Free delivery
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Fluval U3 - Internal Filter
Fluval U3 Internal Aquarium Filter
Free delivery between Tue – Wed
Fluval U3 Internal Filter - Powerful 3-Stage Filtration for Aquariums up to 150L
Free delivery
originally posted on petco.com
I always used external-hang over the back filter systems before Fluval. The first one I bought cleared my water overnight. It lasted for two years or more. I also like how it ads the water oxygenating feature by creating movement on the water surface. The filters and sponges are a bit expensive but I guess it's worth it if it keeps your water healthy.
originally posted on ebay.com
Cleared out turtle tank a lot faster than we expected. Good choice of air flow. Very Quiet Design fits nicely. Am happy with our purchase.
originally posted on hugglepets.co.uk
Not the best filter, I bought this to change from my old 3Plus, I have a 34L tank and the 3Plus was a bit strong for the fish. Since fitting the U1 my water has gone cloudy and isn’t filtering a lot. Obviously the 3Plus is better but the U1 is meant to work for a tank my size.
| Output | 600L |
| Watts | 7.5W |
| Suits | 150L tanks |
| Dimensions | 8 x 9.5 x 27 cm |
Fluval U3 Underwater Filter 150l Clear
Delivery $29.99
Fluval U3 - Internal Filter
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval U3 - Aquarium Internal Filter 600l/h Up To 150l Fish Tanks
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval U3 Internal Fish Tank Aquarium Filter Design
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
Fluval U3 Internal Aquarium Water Filter 600l/h Fish Tank Filtration
Free delivery
Affiliate Disclosure: We may receive a small commission for purchases made through this link at no extra cost to you. This helps support our site. Thank you!
I always used external-hang over the back filter systems before Fluval. The first one I bought cleared my water overnight. It lasted for two years or more. I also like how it ads the water oxygenating feature by creating movement on the water surface. The filters and sponges are a bit expensive but I guess it's worth it if it keeps your water healthy.
Cleared out turtle tank a lot faster than we expected. Good choice of air flow. Very Quiet Design fits nicely. Am happy with our purchase.
Not the best filter, I bought this to change from my old 3Plus, I have a 34L tank and the 3Plus was a bit strong for the fish. Since fitting the U1 my water has gone cloudy and isn’t filtering a lot. Obviously the 3Plus is better but the U1 is meant to work for a tank my size.
I use this filter on my 55 gallon planted tank. The spray bar is perfect for a planted tank. It seems to move the same amount of water as the top and bottom jet but spreads it out so as not to disturb anything. It can be adjusted in three full-forced directions, or it can be carefully set to an "in-between" position for even more gentle flow. I keep it at the end of the long tank, and the water clearly circulates around the entire tank quickly, even on the in-between setting.The intake areas are huge compared other filters, covering two whole sides of the filter. This spreads out the intake so no fry would every get sucked in; however, this also prevents some detritus from being sucked up quickly.This filter handles the biological filter load quite well so long ... MoreI use this filter on my 55 gallon planted tank. The spray bar is perfect for a planted tank. It seems to move the same amount of water as the top and bottom jet but spreads it out so as not to disturb anything. It can be adjusted in three full-forced directions, or it can be carefully set to an "in-between" position for even more gentle flow. I keep it at the end of the long tank, and the water clearly circulates around the entire tank quickly, even on the in-between setting.The intake areas are huge compared other filters, covering two whole sides of the filter. This spreads out the intake so no fry would every get sucked in; however, this also prevents some detritus from being sucked up quickly.This filter handles the biological filter load quite well so long I don't clean both sides of the filter within a week. I don't use the carbon pads, only sponges, and I clean just one each weekend. It has one on each side, so it's simple to maintain biological balance. The biggest problem with this is that a cloud of gunk will spill out when I remove a filter pad. I just make a point to do a water change with a siphon immediately after cleaning the pad and suck out all the gunk.It is completely silent so long as you make a point to remove all air from it.
I had a "old" Fluval filter without the bio stones...and carbon filterit was just the "foam filter" (submersible) and it worked GREAT!When I bought a larger tank for my turtles I purchased a Fluval C3I was breeding mosquito's with this filter....don't ask me how.SO I decided to go back to the submersible filter and of course because I had no problems with the original Fluval filter, I decided to get another.The FLUVAL U Series is horrible. I've had it for about 2 1/2 weeks,I thought because I threw out the gravel at the bottom that this was thereason it was cloudy. So I purchased NEW gravel, "turtle gravel" fromDr. Smith's and followed the directions on the bags. 4 days later, thewater is still cloudy and I have cleaned the filter thinking it was ... MoreI had a "old" Fluval filter without the bio stones...and carbon filterit was just the "foam filter" (submersible) and it worked GREAT!When I bought a larger tank for my turtles I purchased a Fluval C3I was breeding mosquito's with this filter....don't ask me how.SO I decided to go back to the submersible filter and of course because I had no problems with the original Fluval filter, I decided to get another.The FLUVAL U Series is horrible. I've had it for about 2 1/2 weeks,I thought because I threw out the gravel at the bottom that this was thereason it was cloudy. So I purchased NEW gravel, "turtle gravel" fromDr. Smith's and followed the directions on the bags. 4 days later, thewater is still cloudy and I have cleaned the filter thinking it was clogged...no change. Keep in mind I feed my turtles "live food"so this eliminates left over food decomposition. PS, I've had 1 of myturtles for 16yrs.
Ive been using the Fluval U3 filter for my balcony pond which is around 250 litres. So far its been working perfectly and keeping the water crystal clear with no issues. Its been running for around two weeks now so i don't have an extended experience with this pump. I still haven't added any fish since I'm waiting for them to arrive, but I do have a few plants and Fluval volcanic soil and some rocks in the pond. Zero Algae growth. So far so good!
This filter was bought to use in an aquatic turtle habitat. It works pretty well putting out a lot of current, circulating the water well. I have about 15 gallons of water in a 30 gallon horizontal aquarium. The output is adjustable to output the water either at the top, middle or bottom of the filter. I have tried the kind of turtle filters that hang on the back, but none of them put out enough water. Too little circulation.Pros: Good circulation, cleans water crystal clear.Cons: Needs very frequent cleaning (but turtles are really filthy animals!), does not readily accept your own filter media (you need to use the ones from Fluval), Needs to be submerged completely to work well.
I bought the U4 unit for my 55 gal saltwater fish-live rock-corals to replace my penguin hang-on filter. The reviews were all very favorable. The unit is easy to set up doesn't take much room in the tank. It is very very quiet.It works very well as a biological filter.What I don't like is that it doesn't have a strong intake as a mechanical filter. I don't see it picking up the debrie and trash floating around my sand bed. The intake vents are small so any large deitus floating to it sticks to the outside of the unit. Not good as a mechanical filter.The exhaust is almost too powerful although there is an adjustment knob.
This was my first internal filter, purchased for a 29 gallon planted tank.(Purchased the U2) I ordered two, and loved how quiet the filter was. You cannot even hear it running. It appeared to keep the water clean, but maintenance is a pain. The filter pops off the holder (suctioned to the glass) by tilting it forward, but can sometimes be a struggle, and since it's attached to the cord, can get water every where when you try to take it out of the tank. My first filter simply died, with no indication of a clogged impeller. The second filter lasted two months, before I found it dead after a brief power outage. I took it out and cleaned the impeller and this brought it back to life...for another few days. I just found it dead again today. Overall, very dissatisfied ... MoreThis was my first internal filter, purchased for a 29 gallon planted tank.(Purchased the U2) I ordered two, and loved how quiet the filter was. You cannot even hear it running. It appeared to keep the water clean, but maintenance is a pain. The filter pops off the holder (suctioned to the glass) by tilting it forward, but can sometimes be a struggle, and since it's attached to the cord, can get water every where when you try to take it out of the tank. My first filter simply died, with no indication of a clogged impeller. The second filter lasted two months, before I found it dead after a brief power outage. I took it out and cleaned the impeller and this brought it back to life...for another few days. I just found it dead again today. Overall, very dissatisfied with this. Hang on back filters are so much easier to maintain, and while they are noisier, they get the job done so much better.
This filter worked well for a few months. Then I started having a problem with my water clarity for my turtles. I tried everything and nothing would keep the water clear. So I removed this filter and kept the others ones in, and the water cleared up! It has been spewing out debris that I can't seem to get rid of, even after thorough cleaning, new media, running it in clean water, etc. Not sure what to do with it now, you can't THOROUGHLY clean this filter if you develop a problem like mine.PROS:Circulates water well, and did seem to work well in the beginning.CONS:Stopped working after a few months and MUST be used with other types of filers for turtles.Also hard to keep weighed down, the suctions cups are not strong enough/don't stay in place at all. It ... MoreThis filter worked well for a few months. Then I started having a problem with my water clarity for my turtles. I tried everything and nothing would keep the water clear. So I removed this filter and kept the others ones in, and the water cleared up! It has been spewing out debris that I can't seem to get rid of, even after thorough cleaning, new media, running it in clean water, etc. Not sure what to do with it now, you can't THOROUGHLY clean this filter if you develop a problem like mine.PROS:Circulates water well, and did seem to work well in the beginning.CONS:Stopped working after a few months and MUST be used with other types of filers for turtles.Also hard to keep weighed down, the suctions cups are not strong enough/don't stay in place at all. It always manages to float up. It's big too and hard to hide nicely.
| Output | 600L |
| Watts | 7.5W |
| Suits | 150L tanks |
| Dimensions | 8 x 9.5 x 27 cm |
