Penn-Plax Undergravel Filter for 20–29 Gallon Tanks | Clear Water & Aeration

Overview

PENN-PLAX Clear-Free Premium Under Gravel Filter is an air-driven filtration system designed to keep water crystal-clear while preserving a neat aquarium interior. The design emphasizes simplicity with fewer moving parts, making routine maintenance straightforward for most 20 long to 29 gallon tanks.

Whether you keep freshwater or saltwater setups, this under gravel filter works with your substrate to support a balanced environment. When air is pumped through the included air stones and lifts through the tubes, water travels through the gravel and filter plates, then through the Filt-a-Carb carbon cartridges.

How it works

As air and water move through this system, beneficial bacteria can colonize in the gravel and plates, contributing to biological filtration. The carbon cartridges add a layer of chemical filtration, helping to reduce odors and impurities as water circulates.

Key benefits and features

• Low maintenance design with two filter plates and air-driven operation
• Biological, chemical, and physical filtration through gravel, plates, and carbon media
• Built-in aeration: the filter also acts as a bubbler for added oxygen exchange
• All essential parts included: plates, lift tubes, airline tubes, connectors, and carbon cartridges
• Dimensions: each plate 14 in wide by 11.1 in deep; total span 28 in wide; lift tubes extend 13 to 16 in

Practical setup and use

Place the filter under the gravel, connect to an appropriate air pump, and you will have a discreet, efficient filtration system. The dual action helps maintain clear water while preserving the natural look of your tank interior. Color variants of the plates may differ from the photos.

Notes

Colors of the under gravel plates may vary from the product images. This unit is designed for 20 long to 29 gallon tanks and is suitable for freshwater and saltwater environments.