The three pack of Fluval FX4/FX5/FX6 Nitrite Remover Pads provides incredibly effective chemical filtration for freshwater and saltwater environments. The nitrite resin infused pads were designed to trap floating particles such as debris, waste or food, as well as reducing the amount of nitrites found in your water. The pads help to cultivate beneficial bacteria that contributes to a more balanced and healthy water quality. The Fluval FX4/FX5/FX6 Nitrite Remover Pad is great to use for preventing fish loss, outbreaks or chemical spikes and can be replaced monthly or as required after water testing. Designed to be used with the Fluval FX high performance canister filter series.