What is the black water/black spot when Xiaomi Smart Pet Fountain is used?

Solution:
The granular activated carbon filter will produce a small amount of carbon powder during transportation, so please soak it in clean water for 5 minutes / rinse it for 2 minutes (to wash off the floating carbon) before use, so that it can exert a better filtering effect. If the filter element has been cleaned and black carbon spots appear on the top cover, you can use it with confidence after only one water change.
Note: Activated carbon can effectively filter and remove foreign color and odor in water. If eaten by mistake, it can be excreted with feces without toxic and side effects.