Pink mould in the shower: what it is, how to remove it, how to stop it

By Darwin Tile & Grout · Updated 2026-10-17 · Darwin NT

What the pink stuff actually is

Serratia marcescens is an airborne bacterium that is almost everywhere, including in household dust. It is harmless sitting in the air. Give it a film of water and something to eat, and it forms colonies that produce a pink-to-orange pigment. Showers are ideal: warm, wet for hours at a time in Darwin, and coated in the fatty residue from soap, shampoo and skin. That is why it appears first in the corners, on the floor grout near the drain, along the bottom of the screen and on the underside of bottles and shelves.

It is often mistaken for mould because it grows in the same places, and because real black mould frequently grows underneath it. The two need different handling, which is why it is worth knowing which you have.

Removing it from tiles and grout

• Ventilate and wear gloves. It is a bacterium: don’t rub your eyes mid-job.
• Spray with diluted chlorine bleach (around one part bleach to ten parts water) or 3% hydrogen peroxide. Leave it 10 minutes. Never mix bleach with vinegar or ammonia cleaners.
• Scrub the corners and grout with a stiff nylon brush. The pink film comes away easily; what you are really removing is the soap residue it lives on.
• Rinse thoroughly and dry. Rinse with clean water, then squeegee or towel the area. Wet, clean grout regrows pink slower than wet, soapy grout, but dry grout doesn’t regrow it at all.
• Do the bits you can’t see. Unscrew and soak the shower head, wipe the screen track, and rinse the bases of bottles. Those are the reservoirs it recolonises from.

On natural stone (marble, travertine, limestone) skip the bleach and the acids; use peroxide and a soft brush, and rinse well.

If there are black spots under the pink

Pink film wipes off; black mould doesn’t, because it has rooted into the grout. If the corners are still dark after the pink is gone, follow the step-by-step method in how to get mould out of shower grout. If two proper rounds don’t shift it, the staining is inside the grout, and that is a job for a professional shower clean ($159 for a shower recess) rather than more scrubbing.

Stopping it coming back

• Dry the shower after use. A squeegee on the walls and a wipe of the corners removes the water it needs. This matters more in Darwin than anywhere else in the country.
• Run the exhaust fan during and after showers; leave the door open afterwards.
• Rinse the soap away. Residue is its food. A quick rinse of walls, shelves and bottle bases after each shower starves it.
• Seal the grout. Sealed grout holds less water and soap, so it dries faster and the film has less to grip. Clear sealing adds $69 to a shower clean.
• Weekly wipe with a bathroom cleaner. Little and often.