Fluval 404 Foam Insert
These replacement foam inserts are perfect for keeping your Fluval 404 filter running at peak performance. They work hard to provide mechanical straining of particulate waste, so you can enjoy crystal-clear water in your aquarium.
Fluval Foam provides mechanical straining of particulate waste. It prevents particulate waste from prematurely clogging other filter media in the module stack. Although the primary purpose of Fluval Foam is mechanical filtration, biological activity will eventually occur within its pore structure.