What is the green slime in your dogs bowl?

Do you ever look out at your dogs bowl and think… ‘WOW! I swear I only just cleaned that and it’s already harbouring a colony of green gremlins’? Well, I know that I certainly do! With three dogs each contributing their saliva and backwash, the bowl can start looking like a stagnant pond very fast.

A study conducted by the National Sanitation Foundation (NSF) reported that pet bowls came in at number four in the list for places in our homes that contain the most germs. Number FOUR… that’s not far from the toilet bowl!


I have always thought I was being a great puppy mum by cleaning their bowl on a regular basis (when it looked like it needed it), but after doing some research boy was wrong!


Recently, I have learned the do’s and don’ts, what causes it, how to prevent it and how I can make sure I am and doing it right and giving my boys the best. After learning all of this, I needed to share it with you.


Did you know that trouble is already brewing before the green appears! Scary thought isn’t it. Especially if you have young children around like I do that find drinking out the dogs water bowl the best thing EVER!

The slimy coating that you feel when you run your fingers on the inside of your dogs water bowl is called Biofilm. This is a combination of organic and inorganic material from your dogs mouth and saliva. But, Biofilm is not all bad! It is made up of a combination of good and bad components. The good components are actually good for your dog and can help promote good gut health.

The bad components of the Biofilm are what you want to avoid. If the Biofilm is left to grow and multiply like a plague, then you will eventually start to see the dreaded green slime which is actually Algae. Gross isn’t it!

For a lot of dogs, drinking out of a dirty water bowl does not phase them, but if you have a dog like mine that waits for fresh water, then perhaps you are having a lightbulb moment right now just like I did. For so long I have always thought… why are you so picky?! Now I know! I certainly would not drink from a Biofilm and Algae covered glass unless my life depended on it, and I do not expect him to either. 

The video below shows how a dog actually drinks. It is easy to see how saliva is left after every gulp as the excess falls back into the bowl. 



Low levels of Biofilm are not believed to cause a problem, but thick coatings and Algae are known to cause health issues. The Biofilm creates a safe haven for organisms like Listeria, E-Coli and Legionella, which if left uncleaned can allow them to grow to unsafe levels. Overgrowth a Biofilm containing high levels of the bad components have been linked to Urinary Tract Infections, Middle-ear Infections and Bladder Infections.

In short… yes, it can be dangerous to your pet and your household. People that are immune compromised are more prone to being affected by exposure to bad bacteria, which to me also means they should take more care than a healthy adult when cleaning (or playing for a child) bowls. Immune compromised people often include: Pregnant women, elderly people and young children.

But don’t freak out just yet, there are things you can do to improve the health of your dogs water bowl and reduce the risks of Biofilm and Algae forming.



When it comes to food, the type does make a difference for your dogs food bowl. If you are feeding kibble then you will still need to clean it regularly as even though your dog may lick every skerick and crumb out of it, their saliva still remains and will promote bacterial growth.

If you feed your dog a raw diet, then cleaning the bowl very often is a must. Their saliva will still create a haven for bacteria just like kibble does, but as you also have raw meat sitting in there, you increase the likelihood of exposure to Salmonella and Listeria. This is no need for concern if you clean the bowl regularly (after feeding). The risk comes with a dirty bowl left for a period of time and promoting bacteria growth. Just the same is when you cut up meat on your chopping board.

As for what you feed and its effect on the Biofilm and Algae build up in your pets bowl, it is not believed that there is a correlation.

When it comes to bowls, there is a big difference. It is recommended to use either stainless steel or ceramic bowls, not plastic. Plastic can be easily scratched, these indents make an ideal ‘nest’ for the bacteria to set up home and multiply in. Generally, you will see Algae growing where dents and scratches are first.  

The second reason that you want to stay away from plastic is because it is very porous. Being porous means that as it ages it retains germs in the plastic itself, as well as leaching toxins from the plastic into the water it is holding. This is why plastic bowls, in general, are harder to keep ‘clean’ as they age. Think about when you put beetroot into a white container and it is then forever stained pink, this is because it is porous and has absorbed the juice. Imagine what that is doing over time to your dogs bowl and water quality.  


I have always done the simple wash out with hot water and thought… ‘It looks clean so it must be clean’. Apparently, I could not have been further from the truth.  

The most common and easiest ways is to clean the bowl is with hot water and then by placing it in the dishwasher. This is easy and effective if you are happy to share your dishwasher. I have gone through the three best dog bowl cleaning options below. Personally, I find the 3rd option the most suited to our household, and the thought of using bleach on something my dogs will eat off makes me nervous.


If option 3 is the best suited for you and your household, you can make the paste up in advance and store it to save you time when you next clean your dogs bowl. 


I wish I could give a huge YES for this, but unfortunately so long as your dog produces saliva and is drinking out of the bowl then you will not be able to stop it completely.  

In saying that, the type of bowl that you use does make a big difference. As I have discussed above, using a stainless steel or ceramic bowl will help to slow its growth. If you are using a ceramic bowl and it develops any cracks or chips, then you will likely see some increase in Biofilm growth as the cracks would now be providing a safe nesting spot. The bowl would then also become porous and I recommend replacing it.   

The best way that you can prevent the growth of Biofilm is through regular cleaning. I have researched the timeframe a lot, and some say that it is best to clean every day and some say to only clean your dogs bowl once a week.

Here is my theory! In the Biofilm, there are good and bad bacteria, the good bacteria will help promote good gut health in your dog, along with other benefits, and the bad bacteria will have the negative impacts that I have discussed earlier. 

Because of this, I believe that cleaning once a week is sufficient. This will allow your dog to take in the good parts of the Biofilm but remove the bad components before they become out of hand and have a negative impact.  

If you live in a humid area, you will likely need to clean slightly more often, as everything in a humid area grows like crazy. Also, if you are using a plastic bowl or find that your bowl builds Biofilm fast, then you will need to judge the cleaning frequency that suits you, potentially every 2-3 days.  

 At the end of the day, it needs to be the routine that works for you and that keeps your whole family safe. By providing good quality food, clean water and good dental health, what more could your dog ask for. You know that the slobbery cuddles between you, your dog and your children are safe and you can relax with piece of mind.

If you have any experiences that you would like to share, or have any questions, please reach out to me. I would love to hear from you.  

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