The Fluval U Series Underwater Filters provide compact, fully submersible filtration with strong water circulation and flexible installation options. Available in four sizes from 250LPH to 1000LPH, the range covers everything from small aquariums through to tanks up to 240L.
The U Series can be installed vertically against the aquarium wall or horizontally in shallow setups, making them a versatile option where an external canister filter may not be practical. The U2, U3 and U4 provide multi-stage mechanical, chemical and biological filtration, while the compact U1 uses a simpler foam-based filtration system.
Suitable for both freshwater and saltwater aquariums.
Models & Specifications
| Model |
Flow Rate |
Recommended Tank Size |
Power |
Dimensions |
Included Filter Media |
| U1 |
250LPH |
Up to 55L |
4.5W |
10 × 8 × 15cm |
1 × Foam Filter Pad |
| U2 |
400LPH |
45–110L |
5W |
20 × 9 × 10cm |
2 × Foam Pads, 2 × Poly/Carbon Cartridges, BIOMAX |
| U3 |
600LPH |
90–150L |
7.5W |
26.7 × 8.3 × 10cm |
2 × Foam Pads, 2 × Poly/Carbon Cartridges, BIOMAX |
| U4 |
1000LPH |
130–240L |
10W |
33 × 10 × 11cm |
2 × Foam Pads, 2 × Poly/Carbon Cartridges, BIOMAX |
Key Features
✔ Fully submersible internal aquarium filter
✔ Available in 250, 400, 600 and 1000LPH models
✔ Suitable for freshwater and saltwater aquariums
✔ Can be mounted vertically or horizontally
✔ Compact design keeps filtration contained inside the aquarium
✔ Helps provide water circulation and surface movement
✔ Easy-access design simplifies routine filter maintenance
✔ Adjustable flow allows circulation to be matched to your aquarium
✔ Can be used as the main filter in appropriately sized aquariums
✔ Also suitable as additional filtration or circulation in larger setups
Three-Way Flow Control – U2, U3 & U4
The U2, U3 and U4 allow you to choose between three different water outlet options depending on the circulation required:
✔ Top Output – provides strong circulation and increased surface movement
✔ Integrated Spray Bar – creates a gentler, more evenly distributed water flow
✔ Bottom Output – directs circulation deeper into the aquarium
This gives you greater control over water movement depending on your fish, plants and aquarium layout.
Filtration – U2, U3 & U4
Mechanical Filtration
Foam pads trap larger particles, fish waste and suspended debris from the aquarium water.
Chemical Filtration
Poly/Carbon cartridges help remove finer particles, odours and discolouration.
Biological Filtration
BIOMAX provides a porous surface for beneficial bacteria, helping support the aquarium's biological filtration.
U1 Filtration
The compact U1 uses a simpler foam filtration system rather than the multi-stage media arrangement found in the U2, U3 and U4.
Its foam pad captures suspended debris while also providing surface area for beneficial bacteria to colonise, making it a simple and effective option for smaller aquariums.
Perfect For
✔ Freshwater aquariums
✔ Saltwater aquariums
✔ Tropical community tanks
✔ Planted aquariums
✔ Small through to medium-large aquarium setups
✔ Aquariums where an external canister filter isn't practical
✔ Adding additional filtration to an existing aquarium
✔ Increasing water circulation and surface movement
✔ Shallow aquariums requiring horizontal filter installation
Choosing the Right Size
For best results, choose the model based on your aquarium volume, stocking level and the amount of waste produced by your fish. Heavily stocked aquariums or tanks containing larger fish may benefit from selecting the next filter size up.
Flow rates listed are the manufacturer's nominal pump output. Actual flow can reduce as filter media collects debris, so regular maintenance is important for maintaining good circulation and filtration performance.
