Tom Kendrick wrote:
While taking appropriate safety precautions, get some cheap laundry
bleach and apply to the affected areas, typically the floor. Let it
work for a while, then rinse. Follow the dilution directions for
sanitizing.
We get the same buildup periodically in our marble shower. Bleach
kills the bacteria and sanitizes it for a while. Then the shower gets
used and more stuff arrives.

why do you say cheap bleach? or you just mean it's cheap.

yeah, bleach is cheap.

you know bleach does not remove the mass, it just bleaches it to where
you can't see it.
it removes the color, then the bulk becomes transparent..