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What is BioFilm? (Water Mold)

Last modified: March 21, 2018 @ 4:53 pm


BioFilm is used to describe some different growths that are bacterial in nature. The two most frequently seen in pools and spas are commonly referred to as “Pink Slime” and “Water Mold”.

Water Mold and Pink Slime

Water mold is not a single organism. It’s a combination of microorganisms, living in a city-like arrangement in slime. Water mold can be white, grey or even pink (pink slime). The color depends on the ratio of the different microorganisms in the slime. The slime typically grows on surfaces, but it can also break free and look like tissue paper floating in the water.

These slimes are referred to as “biofilms”. Some microorganisms form biofilms easily. Others take a long time to organize themselves into these slimy coatings. Biofilms can be divided into three sections moving out from the surface. The bit closest to the surface doesn’t receive much oxygen, and it doesn’t get a lot of nutrients. The microorganisms in this layer tend to have a different metabolism than the others and their job is anchoring the slime to the surface.

The top layer of the biofilm receives most of the oxygen and gets all the food that floats by in the water. Because these microbes are well nourished, they’re breeders. They continuously spew individual microbes out like a volcano, seeding the water with microbes to float off and establish biofilms elsewhere.

Recent studies suggest that the microbes in the middle layer are in a sort of suspended animation. If anything happens to the lower level, they come out of stasis and start behaving like the microbes in that layer working on keeping the biofilm anchored to the surface. If anything happens to the top layer microbes, the middle microbes will start acting like those, producing other microbes. This suspended animation layer is what makes biofilms so difficult to kill and remove. Their existence in the middle layer of the biofilm shields them from the sanitizer in the water.

These three different layers, along with the protective slime that houses them, provide a defense mechanism for the microorganisms. It allows them to survive should anything happen to any of the layers.

Formation of the biofilms begins with microbes floating individually in the water. This free floating form is called “planktonic” and these organisms are fairly easily killed. But most microorganisms want to be stuck to a surface, and when they bounce onto a surface, they grab on tightly. As that single microorganism sticks to the surface, it starts dividing, forming two microbes. They then divide at a rate that doubles in number every 20 minutes.

When a microbe adheres to a surface, it starts emitting chemicals, akin to pheromones, as a signal for other microbes. As more and more of these microbes are stuck to a surface, more chemicals are emitted. When the signal chemicals reach a high enough concentration, the microbes begin to form a biofilm. At this point, their whole metabolism changes.

The metabolic change results in the microbes excreting the slime and segregating into layers within the slime as outlined above. By the time you can faintly see a slime layer on a surface, there are approximately one million microbes per square centimeter. In the tissue-like masses sometimes found floating in the water, there are trillions or more microbes.

The successful elimination of BioFilm depends on the type of sanitizer being used and several other treatment procedures. See BioFilm in Chlorine or Bromine Pools or BioFilm in SoftSwim Pools for more detail.

This information is designed for use only with the BioGuard® brand products named in this computerized printout, and is correct to the best of BioLab, Inc.’s knowledge. BioLab is not responsible for any use of this printout with products other than the BioGuard® brand products named in this printout, and use of this printout with other products could result in improper or incorrect treatment of the pool water.