Thank you for contacting us. Generally, depending on the stock in the tank, and how often you are doing your partial water changes, you change the cartridge every 3-4 weeks. If you have a large turtle, however, it may be more frequent than that. You do not need to change it before that amount of time, unless it gets so clogged, the filter backflows. Keep in mind, turtles need 10 gallons of water for every inch of shell diameter, and a weekly partial water change of at least 50%. They do produce a lot of waste. A lot of people place them in another container for feeding to help keep the water cleaner.
Date published: 2017-09-23