I figured I might as well re-use this thread to ask the same question about a canister filter. I filled a used canister filter with water & baking soda and let it sit for a while, as well as soaking all the tubing and basically every part of it in a bucket of baking soda water overnight. Since apparently, some dirt is fine, that isn't my worry. But how do I know when the filter is completely sterile and ready for use? I will be getting new filter media.