Bio-wheel assembly replacement parts for Penguin filters. Bio-wheel assembly replacement parts for Penguin filters. Do not replace a bio-wheel unless it is damaged since beneficial bacteria live on it. Discoloration of pleated bio-wheel material is normal and desirable. Irregular rotation is also normal. A bio-wheel rotating at any speed is working to eliminate toxic ammonia and nitrite. 100B (20 gallon aquarium) = 5 L x 5 W x 7.5 H 150B (30 gallon aquarium) = 8 L x 5 W x 6.75 H 200B (50 gallon aquarium) = 9 L x 5.25 W x 7.5 H 350B (75 gallon aquarium) = 15 L x 5.25 W x 7.25 H.