Have you ever seen this pink stuff inside your cat's water dish? It is biofilm, and it is full of harmful bacteria for your cat. The water should be changed each day, but emptying the bowl and refilling (or worse, just topping up the bowl), is not enough. The bowls should be scrubbed with hot, soapy water and rinsed well. Others use a spray bottle with a duluted solution of alcohol and water, but the key is to make sure to rinse the bowl.out thoroughly before refilling with fresh water. Even emptying the bowl and giving it a good wipe with clean, dry paper towel will get rid of that slimy film and cut down on bacteria. Sometimes the slime is pink, sometimes it is even clear, but removing it and keeping the bowl clean is one way you can prevent your cat from developing health problems, such as urinary tract infections