Most hobbyists replace these filter socks once a week or every two weeks. The more often you change your filter socks the better your water quality. Yes, they are washable. You will find the steps to clean and reuse our filter socks on our website: AquaticExperts.com
Once on the website you will see a tab called resources. Click the tab and look for the post "How to Clean Filter Socks and Filter Bags"