Penn-Plax Undergravel Filter for 40-55 Gallon Tanks – 4 Plates (CFU55)

Overview

PENN-PLAX presents the Clear-Free Premium Under Gravel Filter, designed to fit most 40–55 gallon aquariums. This air-driven setup uses an external air pump (not included) to circulate water, delivering a clean, balanced flow while keeping the inside of the tank visually tidy. With fewer moving parts, the system emphasizes simple maintenance and reliable performance beneath the substrate.

Why it stands out

This undergravel system brings together multiple filtration modes to support healthy aquarium conditions without clutter in view. The water passes through gravel and filter plates, then through Filt-a-Carb Activated Carbon Cartridges, enabling a combination of filtration types that work in harmony as air is drawn through the stones and up the lift tubes.

• Biological filtration occurs as anaerobic bacteria colonize the gravel and filter plates, helping natural breakdown processes.
• Chemical filtration is provided by replaceable carbon cartridges, helping to reduce impurities and odors.
• Physical filtration happens as water moves through gravel and plates, aiding clarity.

Aeration plus filtration in one

Because the unit is air-driven, it not only filters but also aerates the water. The result can be better surface agitation and dissolved oxygen levels, all achieved within a compact undergravel design.

What’s included and how it fits

The Clear-Free Premium Under Gravel Filter ships with a complete set to cover a 40–55 gallon tank:

• 4 Filter Plates
• 4 Adjustable Lift Tubes
• 4 Straight Airline Tubes
• 9 Filter Plate Connectors
• 4 Replaceable Filt-a-Carb Activated Carbon Cartridges

Dimensions include four 11.25" x 11.25" plates, for a combined 45" width and 11.25" depth, with lift tubes ranging from 13.25" to 16.5" tall at their bases. These measurements help you plan how the system sits beneath the substrate while maintaining a neat interior look.

Versatility and care

Suitable for both freshwater and saltwater setups, this system emphasizes straightforward maintenance and compatibility with a range of tanks in the 40–55 gallon category. The design prioritizes ease of use, with replaceable carbon media for ongoing chemical filtration and simple rotation of components as needed.

Summary

If you’re seeking a reliable, space-conscious undergravel option that supports multiple filtration modes and adds a gentle aeration effect, this Penn-Plax CFU55 model offers a balanced approach for larger tanks. It’s not a guaranteed solution for every scenario, but it presents a practical combination of filtration, aeration, and modular components for versatile setup and maintenance.