U3 Underwater Filter – Designed for Freshwater and Saltwater Aquariums, Also Ideal for Terrariums and Turtle Tanks

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.

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!

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!

Finalmente acqua limpida,in un acquario da 120 litri sostituito con un altro filtro di capacità più ridotte, e’molto silenzioso ,il flusso è abbastanza delicato non smuove troppo l’acqua fa un ottimo lavoro

Ho appena acquistato un nuovo filtro per il mio acquario e devo dire che sono davvero soddisfatto dei risultati ottenuti. Questo filtro funziona in modo eccellente, garantendo una pulizia costante dell'acqua senza alcuno sforzo. La cosa che più mi ha colpito è la sua silenziosità. Rispetto al mio vecchio filtro, questo è praticamente inudibile. Non solo è piacevole per me non sentire costantemente il rumore del filtraggio, ma anche la mia tartaruga sembra apprezzare la tranquillità. Posso dire con certezza che il mio animale si sente più a suo agio senza interferenze sonore fastidiose. Inoltre, la facilità di pulizia di questo filtro è davvero un punto a suo favore. Basta rimuovere il meccanismo di filtraggio e sciacquarlo con acqua corrente per eliminare i residui accumulati. Non è necessaria alcuna procedura complicata o l'uso di prodotti chimici. È un'operazione rapida e indolore che mi permette di risparmiare tempo e fatica. Ma la cosa migliore di tutte è che grazie a questo filtro, posso cambiare l'acqua del mio acquario con meno frequenza rispetto al filtro precedente. La qualità dell'acqua rimane costantemente alta e pulita, senza dover fare interventi continui. La mia tartaruga sembra molto più felice e il suo ambiente è molto più salubre. Sono davvero contento di aver acquistato questo filtro per il mio acquario. Lo consiglio a tutti coloro che cercano un prodotto efficiente, silenzioso e facile da pulire. Non ne rimarrete delusi!

The unit don't work $5 temu product did a better Don't trust German product are good Buy this product, you waste your money I have one left not use, get it from me for half price

This is a long term review as this exact filter was bought April 2018 and used yearly/monthly/weekly/daily/hourly/minute by minute ever since ! I've been a Fluval customer for decades, I've had a number of their filters with dozens upon dozens of tanks over the years and what keeps on me being loyal? 1. Quality 2. Dependable 3. Does it's job day in day out I've been in the hobby for decades and have kept salt/fresh bare bottom/planted and everything in between. I've given speeches, helped 100's of people in this hobby and in all that time and experience you can easily weed out poor manufacturers and you quickly gravitate to manufacturers who provide that dependability that is DEMANDED with the aquarium hobby. In all my years I've never had any Fluval filter quit working for me. Personally I'm in the underwater/submerged phase of tank keeping I guess you can say. I've converted all my main tanks with the Fluval U series and three tanks have this same Fluval U3 for a few different reasons, most importantly is for it's silent operation. I have a couple tanks in bedrooms and the old HOB Hang On Back type filters tend to let the water drop too far as to create that waterfall noise. Some may like that noise but I call it noise for a reason. With the underwater series such as this U3 there is zero and I mean ZERO noise from the filter. No fish stories here so I included the three U3 series filters as proof. For the filter itself, you can adjust the outflow in various regards, the filter unit itself clips into a holder which is suction cupped to the aquarium glass wall and opening the top door to change filter material is quick and painless. If the filter does not sit well in the filter cage something is just blocking it a tad, most likely it is the power cord so just rerun the cord past the clips on the back of the filter and your good to go again. TIP ► When doing any tank filter maintenance I strongly suggest to turn it off first. When I do filter maintenance I completely remove the entire filter into a bucket and then open it to change out filter pads. I do this because if you change filter pads in the tank and plug the filter back in, debris will shoot out of the filter like a hurricane. Change out filter pads in a bucket, rinse the filter itself in some water and you've minimized the debris hurricane. TIP ► There are 5 basic areas within the filter. 1. The ceramic media. Never clean this part...leave it nice and dirty. Caked in debris isn't needed but if there is just remove that debris, don't try to 'wash' the ceramic rings. They also don't need to be replaced. If they are turning into powder, sure but in all my years I've never had to replace ANY ceramic media ! 2. On either side of the filter there is a course then fine area. The course is the sponge and material is first trapped into this. When you do your REGULAR maintenance squeeze this out in water only. You don't need to replace this as the sponge will last for many, many, many years. 3. The final stage is a bad that 'polishes' the water and this includes activated carbon within that filter pad. In my tanks I don't run activated carbon and I caution against using that in most cases actually, so when my filter pad gets dirty I only squeeze this filter pad out in water and I don't replace it. The filter material's integrity against the plastic filter pad cage will last for years and years. People replace their filter material much too frequently. Sorry aquarium filter manufacturers... But they all tend to advocate replacing the filter material wayyyyy to frequently. Replacing filter materials is a huge profit maker for manufacturers. TIP ► In doing filter maintenance when a filter sponge or pad needs to be rinsed some people state to not use tap water as it contains chlorine and possible chloramine so those people say you should only rinse out filter material in cycled tank water. For my own practice I use tap water and I'm never concerned with the tap water chlorine or chloramine. TIP ► In doing filter maintenance only do ONE SIDE at a time. Since the beneficial nitrifying bacteria is held in the filter material if someone were to 'clean' the entire filter - all filter material, the tank can be put into a mini-cycle. Not really a good thing. Only clean 50% of the filter per time, doing this will give a more chemically stable aquarium. TIP ► A dirty filter is a wonderful filter. While you don't need to live with 50% water flow rate from the original brand new condition, people hurt their tanks by cleaning filters too frequently. The nitrifying bacteria is held in the filter material so cleaning the filter too often will easily cause a mini-cycle which will always put stress on livestock. Crystal clear water = dirty filter. Clean filter = zero cycle. Might sound strange but it's the truth. TIP ► If you hear the word ' cycle ' with this hobby that is in reference to a naturally and beneficial occurring chemical process where ammonia is converted to nitrite and then over to nitrate. A brand new tank will take aprox 30 days naturally for this to happen. At that rough 30 day mark PPM readings will be 0 ammonia, 0 nitrite and a reading of nitrate. In terms of fish you need really nothing for nitrate so your reading can be low however if you have live aquarium plants a reading of nitrate is mandatory. TIP ► In all my impeller filters, right out of the box I use a small dab of 100% pure petroleum jelly and rub it all around the magnetic part of the impeller. This will help with lubrication and a small tweak we can do to even further make the tank more quiet. Not gobs are used just a thin coat. I've done this for a very long time and there have been ZERO negative effects in any of my tanks. If this is not done, that beautiful slime coating found in mature aquariums will form within a couple weeks and naturally coat the impeller. I still just use the petroleum jelly anyways. TIP ► Please be very careful about filter placement especially if someone has fine substrate material especially such as sand. This can easily get sucked into the filter and once it hits the impeller it could easily give a louder grinding sound. When people come to me about grinding filter noise this is the first thing I ask them to check. Make sure the impeller cage is 100% clean of any debris. I typically say no closer than 4" so the substrate bottom when people have those fine grain substrates. Standard type gravel size which I only use, I can let the filter stand right on the substrate itself. TIP ► If by chance you have any sort of filter that the impeller appears to be caked with material and cannot be washed off just use a fine piece of sandpaper. Something like a 200 grit is what I have used in the past to make sure there is nothing 'stuck' on the magnet that can cause unwanted noise. This goes to any brand of magnetic impeller filter. You don't need to grind the magnet away just make the surface clean once again. TIP ► My first tip above talked about a dirty filter being wonderful and people clean it too frequently. This is 100% the case...however if your filter requires cleaning more than every 2-3 weeks then it is not the filter but the tank itself has a maintenance issue. If could very well be a buildup of mulm/detritus from lack of regular tank maintenance. Your filter will collect floating debris however if there is too much floating debris then any filter no matter brand or size will clog. That is our issue not a filters issue of not functioning properly. An aquarium filter's purpose is to COLLECT floating material not to magically make floating material 100% disappear. It is OUR regular maintenance job to remove that collected material. TIP ► A simple way to see if a filter is working properly, HOB, underwater or whatever is if water is being moved by the output. If water is being moved, the filter itself works. If the water is only moving 50% from original flow rates that means it is a very dirty filter that needs our cleaning maintenance...the filter did it's job just fine as it collected the floating material....the 50% flow rate is our issue with tank maintenance. There is much more I can write but I'll cut it off there. Good luck with the hobby, keeping aquariums is a wonderful thing. This brand is legend...please don't let someone else tell you otherwise. ===================== Overall: 10/5 Yes a 10 out of 5. Fluval filters are amazing. Suction power: 5/5 Easy to clean: 5/5 Noise level: 5/5 ===================== Helpful, is how I hope you find my review

I had a cloudy aquarium with a filter priced 400 rs. It had to run for a week to make the water clear and the water flow was strong which made the fish hard to swim on their own. But this filter does magic. With in some hours after installation, the water became crystal clear. The flow is very smooth too.