Since most corals and many fish require at least good water quality, I have always chosen to achieve that through partial water changes and through the use of a good protein skimmer. Whether I am changing water in the store or in one of the aquariums that we maintain outside the store, we are performing a minimum 10% water change per week. In addition, we run protein skimmers to remove excessive nutrients that would otherwise remain in these closed systems and cause potential algae nightmares. Keep in mind that the water changes and the protein skimming each supplement the other.