Fluval U3 Underwater Filter – Designed for Freshwater and Saltwater Aquariums, Also Ideal for Terrariums and Turtle Tanks
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Availability:
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Arrives
Saturday, Jul 4
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Size: U3
Features
- Use as a primary filter for smaller aquariums, or supplementary filter for larger aquariums
- Sleek design with easy grip water control panel and redesigned media cartridge to trap more debris
- Convenient flip-top lid allows for quick and easy access to filter cartridge for maintenance or replacement
- Position horizontally for shallow tanks, larger tanks with low water levels, or to create a decorative waterfall feature or vertically against aquarium wall to create currents or customized flow patterns
- Designed for freshwater, saltwater and reptile environments up to 40 gallons
Description
Fluval U3 Underwater Filter is ideal for use in all aquarium or reptile environments. Use the underwater filter as a primary filter in smaller aquariums or as a supplementary filter for larger aquariums. Fluval Underwater Filters with three-stage filtration are ideal for use in fresh, marine or reptile environments, and are also great for tanks with low water levels. Three-stage filtration with BioMax for superior aquarium water quality, flip- top access for quick and easy cartridge replacement, and three-way flow control make the new Fluval U Series the benchmark in underwater filtration. Stage 1 foam removes large particles. In stage 2, the poly/carbon cartridge traps fine debris, improves water clarity and removes impurities. In stage 3, BioMax provides optimal biological filtration efficiency. For more fish tank accessories, check out other Fluval products including aquarium filters, aquarium heaters, aquarium air pumps, aquarium lights, aquarium rocks, aquarium thermometers, and aquarium stands. Fluval has a wide variety of products that are perfect for your pet fish to enjoy in any large fish tank, small fish tank, saltwater tank or freshwater tank. Fluval broke onto the aquatic scene in 1975 by introducing the world’s first 3-stage filter with synchronous motor technology – a breakthrough that is still applied in the industry today. Since then, Fluval has built a legacy around this pioneering spirit, relentlessly adapting in a changing world to launch innovative aquarium products that remain at the forefront of technology, and which set the bar in quality, style and functionality. Fluval’s mission is not just about building products that mimic the natural world, but inspiring aquarists of all skill levels to enjoy and respect the hobby for generations to come.
Brand: Fluval
Tank Volume: 40 Gallons
Product Dimensions: 12"L x 6"W x 5"H
Item Weight: 2 Pounds
Specific Uses For Product: Indoor
Style: 24 to 40 US Gallons
Color: Black
Included Components: Filter
UPC:
Number of Items: 1
Is Discontinued By Manufacturer : No
Product Dimensions : 10.5 x 3.25 x 4 inches; 1.99 Pounds
Item model number : A475A1
Date First Available : August 19, 2004
Manufacturer : Rolf C. Hagen (USA) Corp.
Best Sellers Rank: #16,776 in Pet Supplies (See Top 100 in Pet Supplies) #131 in Aquarium Filter Accessories
#131 in Aquarium Filter Accessories:
Customer Reviews: 4.1 4.1 out of 5 stars (11,166)
Brand Name: Fluval
Included Components: Filter
Model Number: A475A1
UPC: 015561104753 015561104869
Global Trade Identification Number: 53
Manufacturer: Rolf C. Hagen (USA) Corp.
Manufacturer Part Number: A475A1
Warranty Description: 3 years; Fluval U Series Power Filters are guaranteed against defects in material or workmanship under normal aquarium usage and service for 3 years. We offer a 3 year guarantee on all nonreplaceable parts which means that the filter will be repaired or replaced at the manufacturer's discretion, free of charge, when the complete pump is returned with proof of purchase and postage paid. This warranty does not apply to any filter that has been subjected to misuse, negligence, or tampering. No liability is assumed with respect to loss or damage to livestock or personal property irrespective of the cause thereof.
Item Type Name: HAGEN FLUVAL U3 UNDERWATER FILTER
Unit Count: 1 Count
Specific Uses For Product: Indoor
Smart Home Compatibility: Not Smart Home Compatible
Pet Type: Amphibian, Fish, Reptile
Tank Volume: 40 Gallons
Item Dimensions L x W x H: 12"L x 6"W x 5"H
Item Weight: 2 Pounds
Product Style: 24 to 40 US Gallons
Color: Black
Frequently asked questions
If you place your order now, the estimated arrival date for this product is:
Saturday, Jul 4
Yes, absolutely! You may return this product for a full refund within 30 days of receiving it.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
To initiate a return, please visit our Returns Center.
View our full returns policy here.
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Similar Products
Top Amazon Reviews
Size: U2
There are many choices out there when it comes to filtration for your fish tank. Which of the many choices out there would make the best choice for you? Internal, or external? Are you looking for supplemental filtration, or primary filtration? In most situations, an external filter would be the better choice. Canister, power filter, wet/dry sump, refugium, all have the advantage of not taking up any space inside the fish tank. They are also all capable of holding more media than internal filters. However, some situations make it difficult to install an external filter on a fish tank. For example, if the tank is located in such a way that there are no available spaces behind, nor at the bottom, then your only choice might be to use an internal filter. For simple biological filtration, an air-driven sponge filter would suffice. However, a pump-driven internal filter offers increased circulation and better mechanical filtration. Let us say that you want an internal filter that is capable of providing complete filtration. Not just supplemental filtration but rather a single filter that can provide mechanical, biological, and chemical filtration. In that case, your choices will be limited. Most internal filters are designed to provide supplemental filtration. Most will provide mechanical and biological, but few of the designs will provide chemical filtration. The Fluval U-series of internal filters provide complete filtration, with the exception of the smallest model in the line up. This is the best internal filter that I have ever bought. An internal filter would not be my first choice. However, I was faced with a situation that would not have allowed the use of an external power filter. My choice then came down to between an internal vs. a canister filter. The tank will contain floating plants. Circulation needed to be gentle, and the surface of the water should be still. This filter met the requirements, without the maintenance hassle of having to use a canister filter. The filter was easy to install. The bracket system allows you to remove the filter, without having to remove the suction cups. The suction cups are attached to the bracket, and it is the bracket that holds the filter unit inside the tank. It is surprisingly quiet. You can adjust the output. Water can exit from the top, the middle, or the bottom of the unit. The middle output provides the most gentle flow. Mechanical filtration is provided by a coarse sponge, followed by a fine filter pad. The back of the filter pad is carbonized. This provides a little bit of chemical filtration. Biomax ceramic rings provide the biological portion of the filtration. All in all, a tidy, complete filter system. Disadvantages? It takes up a lot of space inside the tank. The small amount of carbon bonded to the filter pad is not enough to remove tannins from the water. And, it gets used up very quickly. It is possible that you may be able to remove the biomax and put pelleted carbon in its place. Another weakness is that the mounting bracket uses suction cups to attach to the tank wall. A truly modern filter design such as this should be using magnets instead of rubber cups. If you can use an external filter, that should be your first choice. They provide advantages at all three types of filtration (mechanical, biological, and chemical) over even the best internal filter out there. However, if you must have an internal filter, then this is the one that I would recommend. Any of the Fluval U-series, starting with the U2, all the way to the U4 will provide complete filtration. The smallest model, the U1, will not provide complete filtration. Highly recommended. This could be the best internal filter system available in the hobby, in the humble opinion of this reviewer. Please know that I do not own every model of internal filters out there. I am basing this on the ones that I have owned over the years, but there are a few models that I have not tried. However, I have researched the ones commonly available in the U.S., and this line appears to be the best out there. Consider your needs carefully before you decide. If ever Fluval were to discontinue this model, then you will find it difficult to find replacement media. It is not as easy to "create" your own media for this as it would be for an Aquaclear. But it can be done. You can buy bulk padding and cut them to the approximate size and shape of the plastic holder. For carbon, you can simply replace the biomax with large, pelleted carbon.
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Reviewed in the United States on February 22, 2014 by citan-uzuki
Size: U2
The Fluval 2 Water Filter is designed to work in a variety of configurations. This makes it absolutely perfect for tadpole tanks. You can put it sideways, just beneath the surface of the water. This creates a long "basking area" that the tadpoles absolutely love, while at the same time keeping their tank clean. I had no idea the Water Filter would be so ideal when I bought it. Sure, I knew it had a great reputation as a water filter, and that it could create a gentle stream. That is of course the big challenge with tadpole tanks. Tadpoles are MESSY - but they are also tiny and delicate. You want a filter that moves enormous amounts of water in order to keep the tank clean. At the same time, you don't want industrial-strength jets of water blasting into their swimming area. Especially when tadpoles are just developing their little arms and legs, getting hit with that water blast could cause all sorts of damage. The Fluval 2 Water Filter is very easy to set up. You decide what kind of output stream you want, set the speed, and voila. You stick the whole thing into your tank and you're set. I put it in sideways figuring it would take up the least amount of swimming space that way. I was completely shocked when I came back a few hours later and found six of the little tadpoles had wriggled their way on top of it and were soundly sleeping there. At first, I was worried. Would a little limb get stuck somewhere? Would the soft buzzing bother them? But no, it almost seemed soothing. They actively wrestle with each other to get onto that spot and, even if others come and pile on top of them, they lay there contented. It is really cute to watch them. They're like a pile of kittens. The water in the tank is absolutely much cleaner with this running. It does the best one could hope for against the output of these industrious little baby frogs. Highly recommended for tadpoles. Just install it sideways, just below the surface, so the little tadpoles can rest on top of it. There's lots of photos and videos of this in action all through the SuttonMass site. Ask if you have any questions!
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Reviewed in the United States on July 22, 2014 Reviewed in the United States on July 22, 2014 by Lisa Shea
Size: U3
This is one of the best Underwater Filter's that I have found for my turtle tank. Bought for a redear slider. in a 30 gal tank. As soon as I put this in the water, the water cleared up, it is very quiet. The filter is easy to clean. I can get about a month with spot cleaning before I have to pull the filter and do a full clean out. So glad that I found this filter because turtles are very messy!
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Reviewed in the United States on November 5, 2025 by Carrie pitts
Size: U4
__________________________________________________________________________ UPDATED 7/26/12-- see bottom part of entry-- upgrade from 3 to 5 stars __________________________________________________________________________ Original review June 2012: I'm writing a long review because I found it helpful to hear others' experience specifically with turtles. They are a little different than fish when it comes to what works. I have a painted turtle, about 5-6 inches long right now. We have an algae eater too who helps keep the tank clean (we call it a sucker fish, not sure what its real name is). We also periodically add small minnows and goldfish to entertain the turtle and for food if we forget to feed her or go on vacation. Since she's primarily a water turtle, her tank consists of mostly water with a few haul out spots. We just upgraded from a 20G tank to this one. Previously we've always used the Whisper Quiet filters with great success. People would rave about how clean the turtle tank was, and we could pretty much ignore it (don't worry about changing water, etc.) In the 20G tank we had the 20-40G Whisper Quiet in about 16G of water, no plants, a few submerged items, and a floating plastic "log" for basking. For the 50G, we added a few more submerged and surface items, but all are plastic or rocks, nothing living. Upgrading to the 50G tank (with about 40-42G water) posed a problem for me. All of the larger hang on back filters required the water level to be higher than I wanted, since the turtle needs some land, and I didn't want it climbing out. I tried rigging a few up-- the larger Tetra one worked very well, but I had to rig it inside of the tank, and it just took up too much room. I decided to try the underwater Fluval for two reasons-- never need to worry about water level, and because I'm not willing to invest in a canister filter. PROS: --silence. it's golden --ease of changing filter media (it's really simple, you can lift it up so you don't contaminate everything or spit junk back out) --will never dry out or burn out if you lose power and it restarts (since submerged) --ability to place where I like in the tank for optimal filtering and flow to stir things up --ability to change parts of filter at a time to preserve beneficial bacteria --foam pad separate from other pieces so you can rinse that and not everything --no splashing, so no hard water stains on side of tank CONS: --I want to love this filter and I hope it works long term. We used it in a tank that had been recently filled and set up, with the Tetra running for about a week. Initially this worked really well, but about a week into it, the water turned nasty green. First off, TURTLES ARE DIRTY. By nature I don't think this filter accomodates that. I'm holding off judgement since it sometimes takes a while to get things right when you set up a new tank, as it happened before with other filters too at times. However, in this case, I think it's because of a lack of active carbon in the filter. There is just a tiny bit there, and in my experience (6 years with this turtle), the active carbon is ESSENTIAL to keeping them from getting stinky and gross. I decided to remove the bio pellets from the middle part (step 3) since I never had them before in my tanks anyway, and instead fill that space with one of the tetra filters filled with activated carbon. It's been about 10 hours. The nastiness is gone and the tank looks much better. There still seem to be a lot of particles in the water, but I am continuing to work on that-- not sure if I can blame it on the filter at this time. I will keep adjusting, because I think this filter is worth figuring out how to make it work for turtles. I gave it three stars because it advertises that it can be used for my purpose, but I don't think it comes through with the media it uses. I also think their media replacements are expensive relative to other filters (which is especially frustrating when they aren't even working for me). However, if the makeshift adjustment of using other carbon filters inside the third chamber is effective, I would upgrade to 4 stars. If I get to perfectly crystal clear water without the need to pay attention to the tank every week (yes, it's possible with some cheap filters), I'd go to 5 stars. I ask a lot from my filters! ___________________________________________ UPDATE 7/26/12 This definitely deserved the upgrade to five stars. I had to leave for three weeks after adding the Tetra carbon filter to the center in place of the bio pellets, so I filled it with a bunch of minnows for her to eat over time, then came home to a tank that was still crystal clear after 24 days. (Trust me, I was almost afraid to look at the tank when I returned for fear of how gross it might be.) A few minnows were still swimming around happily too. I went ahead and swapped out the carbon filter, but it looks like I can simply wash out the outer sponge and pathetic carbon insert supplied with it periodically and replace the Tetra carbon insert in the center chamber monthly. I still don't like that I had to adjust it, but I don't think there's a great product out there for turtles, and this is working VERY well. Plus, I am now purchasing the cheaper Tetra filters, so my ongoing costs will be less. If you go this route, it does seem like a very tight fit to fold over the Tetra filter and slip it in the middle chamber, so don't be shy. Just wiggle it as you push it in and be gentle. All that remains to be seen is longevity, but for now I am one happy consumer!
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Reviewed in the United States on June 27, 2012 by Patricia L. Horn
Size: U2
I can't actually provide a rating on the performance of the filter itself. It arrived in its usual, timely manner with Amazon's excellent shipping. The shipping package and the display box themselves were in great shape. Upon opening the box, I was treated to a cloud of dust. The bag containing the bio-pellets was ripped wide open and the pellets had disintegrated, coating the unit and the box alike. In addition, one side and the top of the unit looked as if they were kicked around before being packaged. There were scuff marks and deep scratches all over the exterior. Not only did I get a nice dust cloud, in the bottom of the box there were several plastic pieces rattling around. This is never a good sign, but being green in color and the unit itself being black, I didn't think too much of it. That is until we cleaned the unit off, installed it in the aquarium, and turned it on. Nothing happened. It hummed like it was running, but no water was being pulled in or pushed out, even after trying all of the settings. I took the filter out and disassembled to see what was going on. To my surprise, I was able to identify the loose green plastic pieces as the impeller blades. Which means that, unless they used magic plastic, the impeller fan-blades were snapped off prior to the unit being assembled, the broken pieces were dropped into the box, and it was shipped to me. I've been using Amazon since the dawn of...well, Amazon. Never have issues with books, most of the time movies and games come in good shape. Everything else always seems to have an issue, though. My board games had crushed boxes, making them look used. Our sound bar worked for a few months before the optical input and power link functionality just died randomly. Now we order a filter that was assembled broken and shipped. You can roll the dice on this, or just give the money to your local pet store and help them instead.
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Reviewed in the United States on May 1, 2014 by Kyle K
Size: U1
I added the U1 to my 20 gallon tank that already had a 20 gallon filter. I wanted some flow, and extra filtration since I have a few more fish than I should. The sponge covers all inlets, so my Kuhli Loaches and shrimp aren't at risk of being sucked in, which is extremely nice. Any other filter or pump I've used required me to superglue sponges or screens to the inlets. I also love that the sponge is easily removeable via the lid, so I can pull it out and clean it without moving the filter. It also has a removeable piece in the center that I removed and replaced with a media bag full of Zeolite and Carbon blend with some compressed peat for acidity. Mounting the filter was the only downside I had with it, but because of the easily removeable sponge I'm not knocking off a star for it. The U2 and higher models have a bracket, the U1 just has 3 easily removeable suction cups (not a good thing) so once you stick it on the glass, if you even try to move it the tiniest bit to position it just right the suction cups disconnect from the unit and stay stuck on the glass, forcing you to pry them off, pull out the filter, reattach the suction cups, then reposition it again. That said, it stays put, its fairly small, and looks nice. For a filter that attaches to nothing but the wall, it's very quiet. Much more so than the two cheaper units I used. Obviously a HOB will be quieter since it isn't attached to the entire tank turning your tank into a giant vibrating subwoofer, but for something that DOES transmit all of its vibrations straight into the tank its very quiet. My Marina HOB is quieter and the U1 does make a very faint grinding noise, but I can only hear it right next to the tank and 5 feet away it is inaudible. Filtration is great as well. I use it as a second filter, since my HOB is stuffed full of loads of different media so the flow rate is lower, so this serves primarily as a bio-filter to reduce ammonia. For that purpose it does fantastic, and the small media bag in the middle for some extra filtration is nice too. The flow is the best part here though, it keeps my substrate crystal clean and any gunk that gets kicked up by the loaches or cories immediately gets swept into the current and sucked up by the filters. If you're using this as your only filter, definitely add some zeolite and carbon to the middle of it. All said, it's a fantastic filter and I honestly wish I just had one U2 for my 20gal rather than two separate filters.
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Reviewed in the United States on February 23, 2022 by Grant Fowler
Size: U3
The Fluval U3 Filter is a very good underwater filter. It does a good job keeping the water clean. There are adjustable flow vents so you can adjust how you want the water to flow, and you can change it anytime with a turn or a twist. It is very quiet underwater, and changing the filter and filter media is quick and easy. You can do it all underwater pretty much. The filter media can add up if you don't buy it at a good price. Amazon does have some good pricing and some items are sold in bulk which make it cheaper. The bio-media you only change half at a time so to not destroy the cycle you have in the tank. The filter sponge can be squeeze rinsed in a bucket of tank water to remove the yucky stuff at put back. The poly/carbon cartridge i the only think you need to replace completely. You can try to squeeze and rinse out the poly/carbon in a bucket of tank water to buy more time with it, but the poly and the carbon side may both be less effective over time. As mentioned, these things can be purchased in a bulk quantity on Amazon for a great price saving you a lot of money. I recommend the Fluval U3 Underwater Filter because it works great and is very quiet where you here nothing. No more crashing waterfall from your overhang filter. Amazon usually has one of the best prices on the Fluval filters. If you have Amazon Prime, the 2-day Free shipping is a huge money saving plus.
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Reviewed in the United States on March 5, 2016 by BBQ Corn Chips
Size: U1
I had this for a year and finally decided to toss it. I keep my 15 gal tank relatively clean. Had a couple bouts of green algae, but got them shortly under control. Throughout my year, it just an average performance filter in my humble opinion. Some of my smaller fish (tetras and young guppies) met their doom from this, the side slots of the filter are big enough for fish to get sucked into. Also the backside that sticks to the tank, there is enough room for a fish to wiggle it's way back there and get squished or stuck to die. I would clean my filter at least once a month to get optimal performance out of it. That in itself is a PITA (pain in the ass). while the top part is easy, just flips open and you can clean the sponge and the inside, the bottom part where the motor is, gets really jammed (You have to grip the sides, pinch them in and and pull downward at the same time). It takes awhile (sometimes using a towel or help from a stronger person) to get that part dislodged, so you can go in and clean the spinner part. Use a Q-tip to really clean out the canal that holds the spinner fan. Going that extra step will keep it performing well. I did like the bubbles it provided with the tank, to get the water circulating, but after a few months, I was noticing that around 1.5 weeks it was getting gunked up again. Mind you, each tank is different, As part of my maintenance, I do my water changes and vacuum gravel weekly, so including bi-weekly filter cleanings was becoming cumbersome to my tasks (considering what a pain in the ass it was to clean it). I had this filter in addition to another AquaClear Power filter. Aesthetically, it is very bulky to have in an aquarium my size. It took up space and my fishes were getting stuck by it. So I had enough and decided to toss it out for good. I know it's biological filter alternative, but just overall seemed like a hassle to be cleaning it as frequently as my other filter, not to mention a death trap for my fish.
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Reviewed in the United States on October 1, 2015 by Ryki