Marineland Bio Wheel Assembly Replacement for the Eclipse Filtration and Illumination Systems 1, 2 and 3, Marineland Bio-Wheel should not be replaced unless damaged, The water flow from your filter drives the Bio-Wheel, As the Bio-Wheel rotates, beneficial bacteria grow and thrive on its super dense surface, As water flows, the Bio-Wheel eliminates ammonia and nitrite on contact, Irregular rotation of the Bio-Wheel is also normal, Discoloration of pleated Bio-Wheel material is normal and desirable, A Bio-Wheel rotating at any speed is working to eliminate toxic ammonia and nitrite, SKU: RPS23254