What it is & what it looks like:
a naturally occurring fungus (this is NOT a form of Algae; it is animal not vegetable)
white mucous or tissue paper-like substance (sometimes called "toilet paper syndrome")

Pink Slime normally occurs as a "kissing cousin" of White Water Mold.  We often times see Pink slime growing "on top of" White Water Mold - as shown on the pump basket below.

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

can remain a contaminant even after treatment exists on the surface of PVC plastics can re-contaminate long after it appears that it has been destroyed (includes pool & spa toys, floats, spa pillows, steps, hydro-jet rings, filter areas, skimmer baskets, weirs, garden hoses, lights - as shown left, etc.) small quantities can lead to a re-establishment of the problem caused by improper water & pool maintenance, environment, poor circulation prefers areas that are "dark" (not exposed to direct sunlight) & with "slow moving" water is often found alongside of "Pink Slime"

Spa mold gets a hold on your spa due to the growth & spread of bio-films on spa surfaces. Get the details here.

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

Prevention:
Prevention of "white water mold" is preferred over treatment. Follow these steps to help prevent white water mold:
1. Physically brush & clean ALL Pool surfaces weekly, including steps (especially underneath each step) & rails
2. Expose ALL pool surfaces to as much sunlight as possible (sunlight & UV are natural
oxidizers -  often not practical on indoor spas)
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. Regularly add oxidizing chemicals into the skimmer to purge & clean the filtration lines of any bio-film*
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.
6. Regularly clean pool toys & floats
7. Regularly clean pool solar blanket 
8. Chemically clean pool filter every 4 to 6 weeks 
9. Add regular maintenance dosages of "Shock" & Algicide every 2 to 3 weeks as prescribed
10. Use Soft Touch as a preventative 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. Keep the water balanced at all times. Recheck after heavy usage or rain or large "top-offs" of new water. Water balance refers to Free Available Sanitizer level, pH, Total Alkalinity, Calcium Hardness.
15. Use AquaFinesse Pool Pucks to consistently treat & remove the Bio-Film to prevent the growth of White Water Mold & Pink Slim.

Treatment:
Treatment of "white water mold" MUST BE QUICK AND TOTAL! DON'T SKIMP!
1. Clean all pool & affected surfaces as prescribed above.
2. Physically clean & remove all visible "white water mold"
3. Add an initial dosage of algicide to the pool*
4. "Shock" the pool with a triple or quadruple dose*
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
7. Bring in a fresh water sample about 4 days later for a retest & evaluation
8. Maintain Soft Touch levels
9. Maintain good water balance of pH, Total Alkalinity & Calcium Hardness
10. Use AquaFinesse Pool Pucks to consistently remove the Bio-Film to prevent the growth of White Water Mold & Pink Slim (you will notice remarkable differences after about 2 weeks).