The Catit Triple Action filter removes magnesium and calcium from tap water. These minerals can accumulate in your pet’s lower urinary tract and lead to urinary tract diseases, which is a common health issue for cats. Additionally, this high performance filter removes chlorine odours and bacteria and retains stray hairs, sediment and debris. Leaving your cat with crystal clear water that will be inviting to drink. Water softening replacement filters compatible with the Flower Fountain.