The fiber membrane does not wear out and doesn't need to be replaced. To prevent growth of mold, it can be removed, squeezed to remove water, and dried out; or it can be stored in acid water, but don't store it in the unit wet for more than a few days. I have used the same one for 2 years. While in operation, the environment is too hostile for bacteria to grow. Having a spare is a good idea. For purchasers of ionizer only.
