---
product_id: 2333775
title: "U3 Underwater Filter – Designed for Freshwater and Saltwater Aquariums, Also Ideal for Terrariums and Turtle Tanks"
brand: "fluval"
price: "₨2589"
currency: SCR
in_stock: true
reviews_count: 8
category: "Fluval"
url: https://www.desertcart.sc/products/2333775-u3-underwater-filter-designed-for-freshwater-and-saltwater-aquariums-also
store_origin: SC
region: Seychelles
---

# 150L/hr flow capacity 3-stage filtration system 3-way adjustable flow control U3 Underwater Filter – Designed for Freshwater and Saltwater Aquariums, Also Ideal for Terrariums and Turtle Tanks

**Brand:** fluval
**Price:** ₨2589
**Availability:** ✅ In Stock

## Summary

> 💧 Elevate your aquarium game with Fluval U3 — where pristine water meets sleek, smart design!

## Quick Answers

- **What is this?** U3 Underwater Filter – Designed for Freshwater and Saltwater Aquariums, Also Ideal for Terrariums and Turtle Tanks by fluval
- **How much does it cost?** ₨2589 with free shipping
- **Is it available?** Yes, in stock and ready to ship
- **Where can I buy it?** [www.desertcart.sc](https://www.desertcart.sc/products/2333775-u3-underwater-filter-designed-for-freshwater-and-saltwater-aquariums-also)

## Best For

- fluval enthusiasts

## Why This Product

- Trusted fluval brand quality
- Free international shipping included
- Worldwide delivery with tracking
- 15-day hassle-free returns

## Key Features

- • **Effortless Maintenance:** Flip-top lid and easy-grip control panel make filter cartridge swaps a breeze
- • **Crystal-Clear Water, Always:** Advanced 3-stage filtration traps debris, impurities & boosts biological balance
- • **Tailored Flow for Every Tank:** 3-way adjustable output lets you customize water currents or create soothing waterfalls
- • **Freshwater, Saltwater & Beyond:** Engineered for up to 40-gallon tanks, perfect for fish, reptiles, and turtle habitats
- • **Versatile Placement, Maximum Impact:** Use horizontally or vertically to fit shallow tanks, terrariums, or create dynamic flow patterns

## Overview

The Fluval U3 Underwater Filter delivers powerful 3-stage filtration with BioMax ceramic rings, poly/carbon media, and foam to ensure superior water clarity and biological balance. Designed for freshwater, saltwater, and reptile tanks up to 40 gallons, it features a versatile 3-way flow control and a convenient flip-top lid for quick maintenance. Its sleek, compact design fits various tank setups, making it the go-to internal filter for aquarists seeking efficient, customizable filtration without sacrificing style or ease.

## 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.

Review: Internal vs. External Filters - 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.
Review: Our Tadpoles *Love* It - I Posted a Photo - 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!

## 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

## Technical Specifications

| Specification | Value |
|---------------|-------|
| Brand | Fluval |
| Capacity | 150 Liters |
| Customer Reviews | 4.0 out of 5 stars 10,968 Reviews |
| Included Components | Filter |
| Power Source | Corded Electric |
| Product Dimensions | 12"L x 6"W x 5"H |
| Purification Method | Poly/Carbon |

## Product Details

- **Brand:** Fluval
- **Capacity:** 150 Liters
- **Included Components:** Filter
- **Item Weight:** 2 Pounds
- **Maximum Flow Rate:** 600 Liters Per Hour
- **Model Name:** HAGEN FLUVAL U3 UNDERWATER FILTER
- **Power Source:** Corded Electric
- **Product Dimensions:** 12"L x 6"W x 5"H
- **Purification Method:** Poly/Carbon
- **Supported Water TDS Level Maximum (PPM):** 300

## Images

![U3 Underwater Filter – Designed for Freshwater and Saltwater Aquariums, Also Ideal for Terrariums and Turtle Tanks - Image 1](https://m.media-amazon.com/images/I/71x9jM2Xh2L.jpg)

## Available Options

This product comes in different **Size** options.

## Questions & Answers

**Q: Currently have a 10gallon but will upgrade shortly to a 30ish for a yellow eared turtle.  Does this sit on the bottom where it could suck in the food and waste that collects on the bottom where my river rocks are?  It has proven hard to get that out and the pleccu is not cleaning it up as of now.**
A: Mine is laying on the bottom of my tank and i have never had it sitting upright. I can tell you it does pretty well sucking everything up. However, i usually have one spot in the tank, right underneath the filter where debris sits. When I need to water change I just make sure I get the debris out with a fish net. That seems to work pretty well. It is the best filter I have had so far (with a turtle that has killed 4 filters), just make sure to clean the motor fan with every water change or filter media change.

**Q: Does the U4 filter have space to add activated carbon pellets?**
A: Yes it can, in the center of the filter there a removeable plastic cage. I put a small Chemi Pure bag in it. But I didn't care for this filter and not cause it didn't work. But I was wanting something more as a skimmer type filter and I wasn't getting enough flow out this filter unit. But it did work, if your running this on a smaller tank say no 30 gal freshwater ok. I was running it on a 29 gal reef tank with lots of live rock and it couldn't push enough water around it. But it did filter the water good.

**Q: Do all 3 outputs work at the same time?**
A: No, you have to pick a setting. I use mine for moving water in the bottom of my tank. It also seems to be he strongest setting out of the 3 choices

**Q: Can I change the direction of the water coming out of the nozzles? For example directing it upwards instead of horizontal.**
A: There's a small directional piece on the end of each nozzle you can turn to minimally direct the flow - but not nearly that much.

## Customer Reviews

### ⭐⭐⭐⭐⭐ Internal vs. External Filters
*by C***I on February 22, 2014*

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.

### ⭐⭐⭐⭐⭐ Our Tadpoles *Love* It - I Posted a Photo
*by L***A on July 22, 2014*

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!

### ⭐ BUY THIS SOMEWHERE ELSE
*by K***K on May 1, 2014*

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.

## Frequently Bought Together

- Fluval U3 Underwater Filter – Designed for Freshwater and Saltwater Aquariums, Also Ideal for Terrariums and Turtle Tanks
- Nosiny 20 Pieces Filter Foam Pad Compatible with Fluval U3 Underwater Sponge Aquarium Underwater Filter Accessories Compatible for Aquarium, Fish Tank
- Fluval U3 Underwater Filter Poly/Carbon

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*Product available on Desertcart Seychelles*
*Store origin: SC*
*Last updated: 2026-03-10*