Review on 🐠 Fluval U4 Poly-Carb Cartridge - Replacement Underwater Aquarium Filter Media (2-Pack) - A492 by Tracey Brown

Excellent for cleaning the aquarium but poorly removing odors despite the fact that activated carbon is included in the packaging. But to be honest, my planted aquarium has a very tight lid that doesn't let much air in. Chem/Filter changed twice. I also have a Hydor canister filter and cleaning every 6 weeks between filters and water changes. You can rinse these pads with plain tap water as they are not the main source of biological filtration for U4 and will be much cleaner. Then you can exchange one for a new one and move the washed one to the other side.