Water changes dilute toxins that naturally accumulate in the aquarium. There are many philosophies about frequency and volume, but small water exchanges done frequently are generally considered best for maintaining healthy conditions in your aquarium. A 10% water exchange done weekly is ideal, however, changing about 25% of the aquarium water once or twice a month is sufficient for most aquariums. Avoid changing more than 50% of the water in your aquarium. In doing so you can dramatically change the aquarium water parameters (temperature, pH, chemistry). Major changes to the aquarium environment should be done slowly so fish have time to acclimate. Watch our video on The Importance of Water Changes.