"Pink Slime" Causes - some facts & our experience with our customers

As we have mentioned, "Pink Slime" is a naturally occurring bacterium (of the newly formed genus Methylobacterium).  It is NOT pathogenic (not harmful).  This is NOT a form of Algae; it is animal not vegetable.  It is seen/experienced in many places outside of swimming pools.

It is given its name because it is Pink-pigmented and forms a heavy, protective slime coating providing itself with an unusually high level of protection and oftentimes found WITH White Water Mold.  Pink slime is very resilient against halogen-based (chlorine, bromine) as well as non-halogen sanitizers or germicides can remain a contaminant even after treatment. This is NOT a biguanide problem ONLY.  Nor does using "biguanide" based sanitizers cause or contribute to its existence or growth.  That being said, to be truthful, we do see a somewhat larger percentage of biguanide treated pools affected by pink slime as compared to halogen treated pools.

The bacterium has a natural affinity for the matrix that exists on the surface of PVC plastics; it will attach itself to & inside of the matrix, allowing it to 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, etc.). Remaining small quantities of the bacteria can lead to a re-establishment of the problem. Pink Slime prefers areas that are "dark" (not exposed to direct sunlight, such as underground piping, home piping, etc.) & with "slow moving" or "not constantly moving" water.

In swimming pools, pink slime is caused by improper water & pool maintenance, environment, poor circulation to name a few.  After regular tracking of homeowners swimming pools affected by pink slime, we have noted & present some commonalities:

1. There appears to have occurred a dramatic rise in the reported cases of pink slime especially over the past 5 to 10 years. I'll go into more depth with this comment later.

2. Many, but not all, affected pools have "smaller (under) sized" cartridge filters. (i.e. using a 75 sq ft filter on a 24 ft Rnd aboveground pool or a 90 sq ft filter on a 15 x 30 inground pool).

3. Pools get 6 hours or less of direct sunlight on the pool surfaces.

4. Pool owners always leave the solar blanket on AND don't chemically clean the blanket the recommended 2 times per year to remove the accumulated biofilm.

5. "Shocking" or oxidizing of the pool water is not done with the recommended label instructions.

6. Rainy pool seasons see a dramatic rise in the cases of pink slime.

7. Customers regularly add fresh water from their tap without letting the hose-water run for a couple of minutes (slime is present in the garden hose).

8. Pools with sand filters are not changing the sand every 2 to 3 years AND not chemically cleaning the filter sand 3 times a season (once every 6 to 8 weeks).

9. Newer observation, although we've been watching for the past 2 years.  Most of the affected seem to use publicly treated drinking water.

10. Pools filled with well water appear to be not as severely affected.

11. Affected pools are not as fastidiously maintained chemically (water balance, use of Optimizer Plus, Soft Swim Assist), as clean pools.

One of the other common issues that virtually ALL pool owners who experience Pink Slime observe is a more regular need to clean away "similar-looking" stuff in their homes.  They notice an increased need to clean toilet bowls, sinks, shower areas, etc.  It's appears to be the same stuff. 

A second observation is that many water companies across the country, in partial response to "consumer calls" to "get rid of chlorine in the drinking water" are now using mono-chloramines to treat the water (over the past 5 to 10 years).  Mono-chloramines do an essentially good job at treating pathogens in the drinking water, however, some of the non-pathogenic organisms may indeed be getting by.

Unfortunately, we only have experiential or anecdotal evidence.  Having treated literally hundreds & thousands or swimming pools with biguanide systems over the past 20 years, these are our observations.  I don't believe we're that far off base.

Prevention: Click here for preventative measures 


*Follow the instructions given by your pool care specialist EXPLICITLY. Failure to do so could result in harm to you and/or your pool & its components.