"Bio-Wheel Replacement 1/11/06 Q: Great info here. I have a quick question. I am converting my saltwater tank to freshwater. I wanted to see if I could reuse the BioWheels? from my Magnum 350 after rinsing/soaking them in freshwater, or if they will need to be replaced. Thanks for your help. A: Rinse them out and add Bio-Spira from Marineland to the tank and you will be ready to go.-Chuck" - http://www.wetwebmedia.com/FWSubWebIndex/hngonfltfaqs.htm