Have you noticed a fuzzy, pink or orange film developing along your shower tile, grout, or toilet bowl? While many people mistake this for “pink mold,” it is actually a bacterium called Serratia marcescens.
Because this bacterium thrives on moisture and fatty substances (like the minerals in your soap and shampoo), the bathroom is its favorite playground. Here is how to eliminate it and keep it from coming back.
What is Serratia Marcescens?
Serratia marcescens is an airborne bacterium found naturally in soil and water. It produces a red pigment called prodigiosin at room temperature, which gives it that characteristic pinkish-orange hue.
While generally harmless to healthy individuals, it can cause infections in pets or those with compromised immune systems. It is also notoriously difficult to eradicate because it forms a biofilm—a protective layer that acts as a shield against light cleaning.
Step-by-Step: How to Kill and Remove Pink Slime
To truly remove Serratia marcescens, you need to break down the biofilm and disinfect the surface.
1. Safety First
Before cleaning, ensure the bathroom is well-ventilated. Wear rubber gloves and, if you are scrubbing a large area, consider a mask to avoid inhaling aerosolized bacteria.
2. Create Your Cleaning Solution
While vinegar is great for hard water, it isn’t always enough for bacteria. For the best results, use one of the following:
- Bleach Solution: Mix 1 part bleach with 10 parts water. (Best for white grout and porcelain).
- Baking Soda Paste: Mix baking soda with a small amount of liquid dish soap to create a physical abrasive that cuts through the biofilm.
3. The Scrubbing Phase
- Apply your cleaner to the affected areas.
- Let it sit for 10–15 minutes. This “dwell time” is crucial for killing the bacteria at the root.
- Use a stiff-bristled brush or an old toothbrush to scrub the grout lines and corners.
- Rinse thoroughly with hot water.
4. Flush the Drains
Bacteria often hide in shower drains. Pour a mixture of 1/2 cup baking soda followed by 1/2 cup white vinegar down the drain, let it fizz, and flush with boiling water to clear out hidden colonies.
How to Prevent Pink Slime from Returning
Cleaning is only half the battle. Because Serratia marcescens is airborne, it will eventually find its way back into your bathroom. Your goal is to make the environment inhospitable.
| Method | Why it Works |
| Squeegee After Use | Removes the standing water the bacteria need to grow. |
| Run the Exhaust Fan | Lowers humidity levels; run it for 20 minutes after every shower. |
| Switch to Liquid Soap | Bar soap leaves “soap scum” (fatty acids) which is a primary food source for Serratia. |
| Wash Shower Liners | Toss plastic liners in the wash with a little bleach once a month. |
Summary for Homeowners
The key to winning the war against pink bathroom slime is consistency. Because Serratia marcescens feeds on the phosphorus and fatty substances in your hygiene products, regular rinsing of shower walls and maintaining low humidity are your best lines of defense.
Pro Tip: If you have a persistent problem in your toilet, check your water softener. Occasionally, these bacteria can colonize the resin bed of a water filtration system.
