Supurrrb idea! But if you're using a carbon-based filter in your fountain, it can filter our active ingredients. We recommend simply removing the carbon filter. The actively flowing water will still be fresh when using our Pet Dental Water Additive. If you're using a mesh type filter, there is no need to remove it; it will still work perfectly. For the best results, it is recommended to refresh the water every day, or at most every other day.