It's time to change our cartridge filter, and we also need to add a couple of pounds of CYA. I just noticed that the label on the CYA says make sure your filter is clean. Should we dump the cya in (sock method) let it run for a few days, and then change our filter? Or change the filter now and then add the CYA? Note: the filter was cleaned recently but it's making a terrible vibrating noise from time to time so we figured it would be a good time to change the filter.