No, you do not have to do a water change. We recommend rinsing our polishing pads in case there is any dust on the pad from our cutting machines. If there is any dust it will not have any effect on your aquatic animals. We have a lot of hobbyists and aquarium service companies (for many years) who do not rinse our polishing pads, they just cut to size and drop them in their filter. They do not have any problems. So, all is well with your aquatic friends.