Troubleshooting Biofilms, White Water Mold & Pink Slime

Biofilms - the source of so many pool problems

The more we deal with swimming pools and pool problems, the more we realize that  we're dealing with or treating symptoms rather than the root cause of the cloudy  water, algae, scale build up, etc. Not to mention chlorine or sanitizer demand,  excessive need for shocking and so on.

If  you think your pool water is clean and sanitary just because it looks clear,  think again. Yes, you may have shocked the water and added algaecide and even  maintained a good chlorine, bromine, biguanide (Soft Swim or Baquacil) level, but  you've only controlled about 1% of the bacteria in your swimming pool! That's  right, just 1%. The other 99% is on every pool surface that you can or can not  see. And most of those places are virtually impossible to reach. What now?

Whether it's cloudy water, algae,  chlorine demand, scaling, pH & other water balancing issues, Biofilms are most  likely the root cause. 

Biofilms, left untreated, will lead to chlorine (and most other chemicals resistant) White Water Mold & Pink Slime.

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Biofilms can grown almost anywhere there is a surface & some moisture
Biofilms can grown almost anywhere there is a surface & some moisture

Biofilms in general

What are Biofilms & where did they come from?

First, what is a biofilm? A biofilm is a  film or large quantity of bacteria that is living in and as a vast colony in the  microscopic world. In  the "big" world, you could call a coral reef a "biofilm." A biofilm is  self-perpetuating and difficult to remove. Worst of all, biofilm love virtually  any surface, especially wet or damp. But beware, even after drying out, the  biofilm will not necessarily be dead but simply dormant. Did we mention that  biofilms are relatively resistant to chlorine, bromine or other sanitizers?

Second, how do biofilms form? As just mentioned, biofilms form on any  surface. In your pool that means the liner or the pool walls, bottom, ladder  rails, skimmer baskets, ladder treads, filter tank bodies, pump bodies and  impellers, directional returns (eyeballs), heater plumbing, and especially the  piping. There is a 5 steps process as to the formation of biofilms: Attachment,  Colonization, Protection, Growth, and finally what I call Distribution.

Attachment is just that; the bacteria attaches to the surface. It wants a  place to call home and grow. Bacteria want to be in relationships, so they want to find  a nice surface to settle down and join up with a few of their closest friends.

After attaching to the pool surface with their friends, Colonization  takes place as bacteria multiply and divide, growing in number. According to  studies, it is at this crucial point that this attachment is "irreversible." The  bacteria colony is there to stay unless purposefully removed. This stage is  typically accomplished in a matter of minutes or hours at most.

In the Protection stage, the bacteria colony or biofilm begins protecting  itself against invasion. Invasion from environmental factors, "lethal" chemicals  (such as chlorine or bromine), predators, anything that want to destroy it. In  technical terms, the bacteria begins to excrete a protective coating called an  "exopolysaccharide" film. The film is sticky or slimy and very hearty. Now the  biofilm is ready to experience explosive growth.

Growth of biofilms is like a coral reef, the biofilm gets bigger and  tougher. Super colonies of biofilm are actually absorbing certain chemicals that  were meant to destroy them.

Now we come full circle to Distribution  where these broken parts begin to attach to other surfaces or different parts of  the same surface. And the cycle begins anew.

By  the way, biofilms are everywhere. Pools, spas, bathrooms, kitchens, the funky  look to your patio furniture, on your teeth (plaque is a biofilm), wherever  there is a surface that can be damp, you will find a biofilm.

What to do? Resistant to chlorine or bromine. Bonds with biguanides. Ionizers  have no effect. You have to remove it. But how?

How a biofilm colony grows
How a biofilm colony grows

Treating Biofilms

Successfully treating & preventing Biofilms, White Water Mold & Pink Slime

Biofilms can be removed mechanically, chemically or "naturally."  Mechanical removal using vacuums, wall brushes, scrub  brushes, filter cleaners, etcetera, physically remove the biofilm from visible  places.

Visible places would be the filter cartridge itself, filter  tank, vinyl liner, water line,  ladder  treads, skimmer baskets, etc. You can physically handle the object that needs to  be cleaned.  This is one of the reasons why we as Pool Professionals are so  adamant about brushing the pool's surfaces on a regular, weekly basis.   Brushing breaks up and lifts the biofilm off from its cozy environs enabling the  chlorine to kill it and the filter to remove it.  Be careful however to  regularly clean & chemically clean the filter to remove the accumulations of  "filtered" biofilms from the filter media - whether it be sand, DE or cartridge.

Aboveground pools with serious biofilm infestations should  consider just changing the filter hoses. Typically, most aboveground pools have  2 - 9 ft. or shorter hoses as compared to well over 100 ft. of buried inground piping.

Keep in mind that biofilms are a direct contributor to  chlorine demand, causing the pool to use significantly more chlorine, bromine or  biguanides (such as Baquacil or SoftSwim) than if none were present.  Remove the biofilm, remove an  important component to chlorine demand.

In hard to reach places like pool plumbing lines & inside heaters, biofilms need  to be removed Chemically. This is where so much biofilm (and about 99% of  the bacteria) accumulates and thrives.  Biofilm is left alone.  It has  all that it needs - a surface, moisture, and nutrients floating by. Keep in mind  that biofilm doesn't need sunlight - it's not an algae so sunlight is not one of  biofilm's needs. Biofilms do need "warm" water - 90 F or better for optimal  growth, but as long as it's not cold, the biofilm will survive and grow just  fine thank you. 

Tried & true products such as natural enzymes (ActivNzyme Enzymatic Pool Clarifier) "eat up" much of the nutrients and other  waste that contribute to biofilm growth  thereby stunting it. But as biofilms become more resistant and proliferate, a new arsenal of products must be considered & used.  

Newer products such as AquaFinesse Pool Water Care Tablets are added to the pool skimmer and quite rapidly remove  the biofilm from the hidden surfaces.  AquaFinesse  products have been successfully used in the European market and in industrial  applications for several years. As with the physical removal products, loosened  & removed biofilm particles must be filtered out of the water then removed from  the system entirely.  After initial application, you will notice that the  filter becomes rapidly clogged as the filter traps all of that used biofilm.  Cartridge and diatomaceous earth (DE) filters must be chemically cleaned to restore  the filter to a proper working condition.

If biofilm removal has never been done before, it may be necessary or even advantageous to replace the filter  media (sand, cartridge or DE) - especially in older swimming pools.  These products are completely  compatible with all pool care chemical systems (chlorine, bromine, biguanides,  ionizers. salt). 


AquaFinesse works with ALL pool chemical care systems including  chlorine, bromine, ionizer (Nature2®  & Frog®) and salt  systems as well as all biguanide products such as BioGuard®  Soft Swim® or Arch  Chemicals®  Baquacil®. Other  biofilm removal products are NOT compatible with biguanides.

The bottom line for the pool owner and customer is a longer life of the pool & pool equipment (filter, heater, rails, ladders, etc.) due to  the removal of biofilms as well as biofilm scaling. Chemical consumption should  and will show a marked decrease as chlorine, bromine & other sanitizers can  concentrate on the 1% of planktonic bacteria present in the water. Easier water  balance, less shocking, etc.

Biofilm, White Water Mold & Pink Slime are resistant to chlorine, bromine, shock treatments
Biofilm, White Water Mold & Pink Slime are resistant to chlorine, bromine, shock treatments

Before & After Treatment Examples of Pool Mold

Before - Tile & Grout


After years of "normal" maintenance, ugly biofilms grow turning white grout black or gray.

After - Tile & Grout


Using PoolSpaGuru's recommended treatment, after about 4 to 6 weeks with no additional scrubbing. Our products WORK!

Minimum Treatment

AquaFinesse Pool Water Care Tablets & ActivNzyme work in the removal of biofilms, WWM & Pink Slime

PoolSpaGuru's basic recommended treatment includes AquaFinesse Pool Water Care Tablets and ActivNzyme Enzymatic Clarifier & Phosphate Remover.

Before - Inside a Filter Tank


This biofilm was a sticky, crusty film that had to be scraped off with a knife that had accumulated "naturally" over several years of regular pool use.  

After - Inside a Filter Tank


Using PoolSpaGuru's recommended treatment, the inside of the filter tank is "like new" and clean.  

Recommended Treatment

BioGaurd Optimizer Plus, ActivNzyme & Aquafinesse Pool Water Care Tablets

PoolSpaGuru's recommended treatment includes AquaFinesse Pool Water Care Tablets, ActivNzyme Enzymatic Clarifier & Phosphate Remover, and BioGuard Optimizer Plus.

White Water Mold (WWM), aka Pool Mold, Pool Snot, etc

What WWM is & how to treat it

White Water Mold (WWM) is a naturally occurring fungus (this is NOT a form of Algae; it is animal not  vegetable), that has  a white mucous or tissue paper-like substance  (sometimes called "toilet paper syndrome"). 

WWM forms a heavy, protective coating providing the organism with an unusually high level of protection that is very resilient against halogen-based (chlorine, bromine) & non-halogen sanitizers or germicides. In other words, heavy shocking is not going to solve the problem.

White Water Mold or Pool Mold can remain a contaminant even after treatment exists  on the surface of PVC plastics.  It can re-contaminate long after it appears that it has been destroyed  (includes pool toys, floats, ladders, steps, fountains, automatic pool  cleaner parts, skimmer baskets, weirs, directional fittings, garden  hoses,  lights - as shown left, etc.)

Even small quantities  of Water Mold can lead to a re-establishment of the problem WWM is typically caused by improper water & pool maintenance, environment,  and poor circulation.  

WWM is a "overgrowth" of naturally occurring  Biofilms found on pool surfaces & hiding in areas that are not easily accessible  to regular cleaning such as pipe lines, ladder & handrail tubing, underneath  drop in steps, light niches, etc. Read more about Biofilms above.

White Water Mold is often found lurking in "dark" areas of the pool with poor circulation and sometimes with "Pink Slime". 

PoolSpaGuru's recommended treatment using AquaFinesse along with ActivNzyme will continually  removes the biofilms that grow on ALL pool surfaces leading to Pink Slime &  White Water Mold. AquaFinesse & ActivNzyme are both 100% compatible with ALL pool water care  systems.

White Water Mold IS NOT CAUSED BY  USING BIGUANIDES (Soft Swim, Baquacil, Polyclear, etc.)! It is an environmental issue.

White Water Mold on the backside of an underwater light
White Water Mold on the backside of an underwater light

Pink Slime, aka Pink "Algae"

What Pink Slime is & how to treat it

Pink Slime is a naturally occurring bacterium (of the newly formed genus Methylobacterium)  (this is NOT a form of Algae, it is animal not vegetable). It is Pink-pigmented, forms a  heavy, protective slime coating providing the organism with an unusually  high level of protection, methanol consuming,  oftentimes found WITH White Water Mold. Like WWM, Pink Slime is not pathogenic.


Pink Slime is very resilient against halogen-based  (chlorine, bromine) as well as non-halogen sanitizers or germicides and can remain a contaminant even after treatment.

This is NOT a biguanide problem only! Pink slime can & does occur in  chlorine & bromine pools as well.  The Pink Slime bacterium has an affinity for the matrix that exists on the surface of PVC plastics (it likes it); it will attach itself to & inside of the  matrix, allowing it to recontaminate long after it appears that it has been destroyed (includes pool toys, floats, ladders, steps, fountains, automatic pool cleaner parts, skimmer baskets, weirs, directional  fittings, garden hoses, etc.). For example, when you're closing or winterizing your pool and you notice pinkish "stains" on various pool parts, you MUST thoroughly clean those parts. If you don't clean those parts, when they are re-installed the following spring, the Pink Slime will again flourish.

Small quantities of Pink Slime can lead to a re-establishment of the problem.  It is generally caused by improper water & pool maintenance, environment, poor circulation. 

Pink Slime prefers areas that are "dark" (not exposed to direct sunlight) & with "slow moving" water  (poor circulation).

Consider using Slime Stop spray on ladder treads, skimmer baskets & weirs, eyeballs and other areas where Pink Slime likes to grow.

** In another industry, medical technology, this bacterium occurs  regularly in laboratory tubing   

Pink Slime & White Water Mold IS NOT CAUSED BY  USING BIGUANIDES (Soft Swim, Baquacil, Polyclear, etc.)! 

Pink Slime is an environmental issue. Keep  in mind that Pink Slime CAN be physically removed (comes off with brush or  fingers).  If what you think is Pink Slime, but appears to be more PURPLE &  isn't removed by brushing, you have another problem called Purple Cyanurate.  Click here for the details.

Pink Slime overwhelming pool pump basket
Pink Slime overwhelming pool pump basket

Prevention & Treatment

How to Prevent & Treat White Water Mold & Pink Slime

Prevention:  Prevention of White Water Mold" or Pink Slime is preferred over treatment. Follow these steps to help prevent WWM & PS:  

  1. Physically brush & clean ALL Pool surfaces weekly, including ladder steps (especially underneath each step) & rails 
  2. Expose as many pool surfaces as possible to as much sunlight as possible (sunlight & UV are natural oxidizers)  
  3. Remove the lid from the skimmer to allow sunlight into the basket for several hours each day ** INGROUND POOLS MUST USE EXTREME CAUTION in doing this in order to avoid a person falling into or otherwise injuring themselves due to an open skimmer.
  4. Use PoolSpaGuru's recommended treatment of AquaFinesse & ActivNzyme 
  5. When adding make-up water from the garden hose, allow the water to run for 2 to 3 minutes before putting the hose into the pool (WWM grows there too). 
  6. Regularly clean pool toys & floats (use Stow Away)  
  7. Regularly clean pool solar blanket (use Stow Away)  
  8. Chemically clean pool filter every 6 to 8 weeks (use Strip Kwik, Kleen It or SoftSwim® Filter Cleaner or Filter Perfect)  
  9. Maintain overall good water care by following the 5 Keys.  
  10. Use BioGuard Optimizer Plus® as a preventive measure  
  11. Run the filter a minimum of 12 hours daily to prevent "dead spots" in the pool.  
  12. Remember to clean & rinse the brushes, hoses & vacuums that you  use to clean the pool 
  13. Leave as much of your pool equipment exposed to the sun.  
  14. Use Slime Stop spray on ladder treads, skimmer weirs & other plastic surfaces to impede the growth of biofilms on those surfaces

Treatment:  Treatment of White Water Mold or Pink Slime MUST BE QUICK AND TOTAL! DON'T SKIMP!

  1. Clean all pool & affected surfaces as prescribed above.  
  2. Physically clean & remove all visible WWM & PS  
  3. Follow PoolSpaGuru's recommended treatment schedule of AquaFinesse, ActivNzyme & Optimizer Plus   
  4. "Shock" the pool with a triple or quadruple dose of your regular shocking product (to kill excess bacteria and restore a chlorine or bromine level)  
  5. Run filter 24 hours daily until water is clear & halogen or peroxide levels are maintained at a "higher" level*
  6. Chemically clean the filter after 2 weeks. THIS STEP IS VERY IMPORTANT to remove the accumulated "dead" mold and slime from the filter. Not cleaning the filter can lead to a faster re-infestation of the mold & slime.   
  7. Maintain good water balance of pH, Total Alkalinity & Calcium Hardness  

1,2,3 punch to treat & prevent biofilms, WWM & Pink Slime! Optimizer Plus, AquafFinesse & ActivNzyme
1,2,3 punch to treat & prevent biofilms, WWM & Pink Slime! Optimizer Plus, AquafFinesse & ActivNzyme

One More Thing

Please understand this about White Water Mold & Pink Slime...

I hate to tell you, but because White Water Pool Mold & Pink Slime are environmental problems and not just swimming pool problems, we find these growths literally everywhere around us in our homes and work places.

Because they're intricately linked to biofilms, WWM & PS will dog you.

Once you begin treating, you MUST always treat. WWM & PS can be well controlled but unfortunately never eliminated. Ever. 

Pink Slime in a toilet bowl. It's not just a pool problem!
Pink Slime in a toilet bowl. It's not just a pool problem!

Download a FREE brochure

Free brochures for you to download: 

Biofilms, 5 Pillars 3 Foundations, ActivNzyme

How to use AquaFinesse in: small pools (up to about 5,000 gallons), pools up to 15,000 gallons (15K), pools up to 20,000 gallons (20k), 

pools up to 30,000 gallons (30k), pools up to 40,000 gallons (35k)