The filter is not required for normal operation of the fountain, but it does significantly improve the overall cleanliness and taste of the water for your pets. The filter removes bad tastes and odours to improve the taste of the water and catches hair and small particles to keep the water cleaner.
The charcoal filter removes bad tastes and odours from the water and catches large particles and debris from re-circulating back into the water. The filters do not purify the water. Change them every 2-4 weeks, depending on how many pets use the fountain, to keep the fountain water fresh and clean.
The charcoal filter should be changed every 2 to 4 weeks, depending on the number of pets using the fountain. If you have more pets or notice more debris, a slimy feel, or decreased water flow in your fountain, you should clean it more often. Pre-filters can usually be changed less frequently.
This black stuff is loose charcoal from the filter and is completely harmless for your pet to drink. The charcoal filter is made of organic coconut shells. Rinse the filter in cold water before placing it in the fountain to prevent this. Some filters may shed more charcoal than others due to differing consistency of charcoal in each batch of filters, so don't be surprised if some filters leave behind more charcoal dust than others.
The charcoal filter removes bad tastes and odors from the water and catches large particles and debris from re-circulating back into the water. Over time, debris gets stuck in the outer fabric of the filter, making it more difficult for the water to pass through it. The inner part of the filter contains granulated carbon with hundreds or thousands of microscopic holes, which bind to impurities in the water that cause bad tastes and smells. This binding prevents impurities them from returning to the water. Eventually, the holes become clogged and can no longer remove impurities.