Hi everyone. I have a 10 gallon quarantine tank that is empty (without fish) for most of the time. I occasionally put one of my angelfish there when she's fighting with my other angelfish. It's filtered all the time. The filter I have is a Tetra Whisper Power Filter for 10 gallon tanks. The only media insert it has is carbon that you need to change approx. every month. And I do change it every moth, even though there are no fish. My question is, since there are no fish in that tank, is it really necessary to change the carbon insert every month? There are no wastes when there are no fish. How often should I change the carbon insert in a quarantine tank (without fish)? Below is the picture of the filter I have.