On my tanks that run a HOB I rinse the media in the old/dirty tank water every week during my normal water changes. I don't replace the filter pad until/unless it's falling apart, though. There is a lot of beneficial bacteria that can colonize in your filter. If you're removing it every week, it can be difficult for the bb to colonize, and you *might* have a less stable tank as a result. I've actually replaced the brand filter pads with foam aquarium sponges. They do the required job nicely and last forever. Since I never have to change out my media, the bacteria is allowed to grow and thrive.