The Fluval FX Series Filter Elements are precision-engineered media packs designed exclusively for FX2, FX4 and FX6 high-performance canister filters. They combine mechanical foams, biological bio-rings and chemical carbon/zeolite inserts in layered trays to maintain factory-level filtration flow, support beneficial bacteria growth and efficiently remove ammonia, nitrite, heavy metals and discolouration in both freshwater and marine aquariums. These media elements should be replaced or refreshed according to tank load and water test results to ensure optimal filter performance and longevity. Fluval Bio‑FX Biological Media