Fluval U3 front view illustrating a compact, versatile underwater filter for small tanks.
Fluval U3 stage 1 foam filter capturing large debris for cleaner water.
Fluval U3 stage 2 poly/carbon cartridge trapping fine debris and impurities.
Fluval U3 BioMax media promoting beneficial biological filtration in aquariums.
Fluval U3 flip-top lid enabling quick cartridge access for maintenance.
Fluval U3 three-way flow control for personalized current in tanks.
Fluval U3 front view illustrating a compact, versatile underwater filter for small tanks.
Fluval U3 stage 1 foam filter capturing large debris for cleaner water.
Fluval U3 stage 2 poly/carbon cartridge trapping fine debris and impurities.
Fluval U3 BioMax media promoting beneficial biological filtration in aquariums.
Fluval U3 flip-top lid enabling quick cartridge access for maintenance.
Fluval U3 three-way flow control for personalized current in tanks.

Fluval U3 Underwater Filter for Freshwater, Saltwater & Reptile Tanks | 40 Gal

The Fluval U3 Underwater Filter is a compact, versatile filtration solution designed for both aquatic and terrarium...
Availability: In stock
Product type: Filter Accessories
$97.51
$97.51
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Subtotal: $97.51

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Fluval U3 front view illustrating a compact, versatile underwater filter for small tanks.

Fluval U3 Underwater Filter for Freshwater, Saltwater & Reptile Tanks | 40 Gal

$97.51
Fluval U3 front view illustrating a compact, versatile underwater filter for small tanks.
Fluval U3 stage 1 foam filter capturing large debris for cleaner water.
Fluval U3 stage 2 poly/carbon cartridge trapping fine debris and impurities.
Fluval U3 BioMax media promoting beneficial biological filtration in aquariums.
Fluval U3 flip-top lid enabling quick cartridge access for maintenance.
Fluval U3 three-way flow control for personalized current in tanks.

Fluval U3 Underwater Filter for Freshwater, Saltwater & Reptile Tanks | 40 Gal

$97.51
Description
Description
x

The Fluval U3 Underwater Filter is a compact, versatile filtration solution designed for both aquatic and terrarium setups. It works well as a primary filter in smaller tanks or as a reliable supplement in larger aquariums, helping to support clearer water and balanced conditions. Built for freshwater, saltwater, and reptile environments, the U3 brings three-stage filtration and a modern, easy-to-use design to a range of hobbyist layouts.

Three-stage filtration that adapts to your tank

Three distinct stages tackle debris and support filtration performance, so you can enjoy healthier-looking water without complex upkeep.

  • Stage 1: foam captures larger particles, helping reduce cloudiness
  • Stage 2: poly/carbon cartridge traps fine debris and impurities while aiding clarity
  • Stage 3: BioMax media supports beneficial biological filtration for a balanced system

Easy maintenance and flexible layout

Maintenance is built into the design with a flip-top lid for quick cartridge access and straightforward replacement. The media cartridge has been redesigned to trap more debris, and the water control panel offers a comfortable grip for precise adjustments. You can position the unit horizontally for shallow tanks or vertically along the wall to create currents or a subtle waterfall effect, enabling customized flow patterns without taking over the space.

Versatile for freshwater, saltwater, and reptile environments

Designed to perform across different environments, the U3 suits freshwater, saltwater, and terrarium or turtle tanks up to 40 gallons. Whether you’re stabilizing a compact community setup or shaping water movement in a larger display, this filter aims to support clearer water and stable filtration without dominating the scene.

What you gain with Fluval

  • Compact, adaptable design for a range of tank sizes
  • Three-stage filtration with BioMax to support debris removal and bio-filtration
  • Easy cartridge access and maintenance-friendly construction
  • Flexible placement options to tailor flow and ambience

FAQ

Q: Is the Fluval U3 suitable for both freshwater and saltwater tanks?

A: Yes. The U3 is designed for freshwater, saltwater, and reptile setups up to 40 gallons, offering flexible filtration.

Q: What maintenance does the Fluval U3 require?

A: It features a flip-top lid for quick cartridge access and straightforward rinsing, with three-stage filtration to trap debris and support bio-filtration.

Shipping & Return
Shipping & Return
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Shipping

  • Free shipping on all U.S. orders, with no minimum purchase.
  • Orders are processed within 1–2 business days after payment confirmation; weekend and holiday orders are processed on the next business day.
  • Estimated delivery: 3–5 business days after dispatch in most U.S. locations; remote or limited-service areas may take longer.
  • Once your order ships, you receive a tracking link by email; tracking usually becomes active within 24–48 hours.

Returns

  • 30-day returns from the delivery date with a full refund for unused items in their original condition and packaging.
  • Free return shipping: email petlywox@gmail.com with your order number and we send you a prepaid return label.
  • Damaged, defective, expired or incorrect items are also returned free of charge for a full refund — please include photos.
  • Your refund is issued to the original payment method within 10 business days after we receive and inspect the return.
  • Opened food, treats or supplements, used grooming or hygiene items, custom products, sale items and gift cards are not returnable unless they arrived damaged, defective, expired or incorrect.

Full details: Shipping Policy · Refund Policy. Questions? Email petlywox@gmail.com.

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Check the exact measurements and package contents before ordering. Read U.S. delivery details and return conditions. For a product question, email petlywox@gmail.com.

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