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Home > Cats > Why Does My Cat’s Water Bowl Get Slimy? 3 Vet-Approved Reasons

Why Does My Cat’s Water Bowl Get Slimy? 3 Vet-Approved Reasons

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Dr. Marta Vidal-Abarca

Veterinarian, BVSc GPCert (Ophthal) MRCVS

The information is current and up-to-date in accordance with the latest veterinarian research.

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There is nothing we dislike more than picking up the cat’s water bowl and finding a slimy mess. The thought of our pet drinking strange-colored gunk in the water makes our skin crawl. The slimy coating that forms on your cat’s water bowl is called biofilm, and there are three possible reasons it is growing in your cat’s water bowl.


The 3 Possible Reasons Your Cats Water Bowl Is Slimy

1. Unsatisfactory Cleaning

If you continually refill your cat’s water bowl without washing it, you may be allowing bacteria, food remnants, and saliva to remain in the bowl. The build-up of these substances will cause slime to grow in your feline’s water bowl. Insufficient cleaning can also leave bacteria in the bowl to grow and become biofilm.

2. Cats and Other Pets

If you have a multi-pet household and they are sharing a water bowl, the bacterium from their tongues is dripping into the water bowl. The more animals drink from the bowl, the quicker the slime will grow, and biofilm will form.

Red Shiba inu dog and red cat lying on gray couch
Image by: Egrigorovich, Shutterstock

3. Stagnant Water

As the cat’s water bowl is left standing throughout the day, the water adjusts to room temperature and becomes the ideal breeding ground for bacteria to grow.


How to Prevent Slime in Your Cat’s Water Bowl

Here are some things you can do to prevent the growth of bacteria in your cat’s water bowl.

1. Clean the Bowl

If you only have one cat or pet, it is important to clean your pet’s water bowl at least once a week. That is the bare minimum. For households that have multiple pets drinking from the same bowl, it is recommended that you clean the bowls a minimum of once daily. This is also recommended for large water containers or automatic waterers that store unused water. When possible, throw the bowls in the dishwasher to help rid them of harmful germs.

2. Outside Cats

If you have cats that live outside, the bowl should be cleaned daily. Slime can grow faster outdoors since there is more bacteria in the environment. Thoroughly clean the bowl to avoid bacteria being left inside.

Havana Brown Cat
Image by: Outside, Shutterstock

3. Non-Porous Bowls

The best surface material for cat bowls is stainless steel. Porous bowls like plastic and wood have small pores that can harbor and trap bacteria and creates a breeding ground for biofilm. A 2018 study by Hartpury University revealed that dangerous bacteria were more likely to thrive in plastic and ceramic bowls than those made from stainless steel.


What Is That Slime in My Cat’s Water Bowl?

As mentioned earlier, the slimy substance that you see on the bottom of your cat’s water bowl is called biofilm. Biofilm is made up of good and bad bacteria that gets into the water from your pet’s saliva, fur, skin, and the environment. The bacterium forms a sticky, slimy substance that contaminates water. The substance can appear in pink, yellow, red, orange, purple, brown, green, black, or clear.

The biofilm may have a foul smell not noticeable to pet parents. So, if you see your feline sniff the water and walk away, you may want to clean the bowl and refill it with fresh water.



Like humans, your cat deserves to eat and drink out of clean bowls. We know life is busy, and sometimes we slack off. Unfortunately, it is not healthy for your cat to drink from a water bowl that has slimy biofilm in it. You should wash the water bowl or fountains routinely and use materials like stainless steel. You may also want to buy more bowls so you can rotate them daily. It is not only our job as pet owners, but we also love our pets and want to keep them safe and healthy.

Featured Image Credit: Vershinin89, Shutterstock

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