The Fluval C4 Power Filter is a high-performance hang-on-back filter featuring a 5-stage filtration system. It uses two mechanical stages (foam pad and poly/foam pad) to remove debris, a large activated carbon insert for chemical filtration, and both a Bio-Screen and C-Nodes for extensive biological filtration. This results in superior water clarity and purity. The C4’s flow rate is adjustable, and its modular design makes maintenance easy, providing reliable, multi-stage filtration for aquariums up to approximately 70 gallons.