Fluval Underwater Filter

Fluval® U Series Underwater Filters provide complete and efficient 3-stage filtration, including BIOMAX biological filtering (U2, U3 and U4 models), to create superior aquarium water quality.

The complete line, consisting of Fluval® U1, U2, U3 and U4 Underwater Filters, includes many practical and versatile features that make them ideal for application in fresh, marine and reptile environments.

Fluval U series filters provide the option of setting the flow output in 3 different positions, a key benchmark in underwater filtration. The Adjustable 3-Way Flow Control feature (U2, U3 and U4 models) lets you position the water flow output to meet your specific needs. The Top Output setting provides maximum circulation and oxygenation, the Integrated Spray Bar setting provides a gentle, even flow for planted aquariums, and the Bottom Output setting is for deepwater agitation.

Fluval® U Filters also include a convenient flip-top lid that allows quick and easy access to the filter cartridge for maintenance or replacement including Fluval’s Clean & Clear cartridge (A499). Packed with special high performance resins, Clean & Clear is proven to reduce phosphate and nitrate while preventing the spread of algae, providing you with a cleaner, clearer aquarium and healthier fish for longer intervals.

Clean & Clear can also be used in U1 filters with its specially designed foam cut out section.

In addition, Fluval® U Filters offer installation versatility: they can be installed vertically against the aquarium wall to create currents or customized flow patterns; or they can be placed horizontally in shallow water tanks or to create decorative features such as waterfalls.

The Fluval® U1 Underwater Filter is ideal for use in fresh, marine or reptile environments. Use the U1 as a primary filter in smaller aquariums or as a supplementary filter for larger aquariums. It is also ideal for tanks with low water levels. The U1 includes an adjustable flow control and comes complete with 1 foam pad.

Available in:
Fluval® U1 is suitable for aquariums up to 55 L (15 U.S. gal.).
Fluval® U2 Underwater Filter, for aquariums from 45 to 110 L (12 to 30 U.S. gal.)
Fluval® U3 Underwater Filter, for aquariums from 90 to 150 L (24 to 40 U.S. gal.)
Fluval® U4 Underwater Filter, for aquariums from 130 to 240 L (34 to 65 U.S. gal.)