I am pretty experienced with aquariums...have had several for a good 6 years now. However, my DH thinks I'm crazy when I tell him that you do not need to replace the Bio Wheel in an aquarium. Our two goldfish recently died, and we have decided to switch to a tropical freshwater setup. DH is thinking you need to change the Bio Wheel between fish setups, but I have changed fish (from comets to goldfish) without any problems. Anyone have any ideas that I can use to convince him we DO NOT need to change the Bio Wheel?