10% Off In-Stock & Special Order Furniture
Pool supply sale - SAVE UP TO 20%!
20% off Playsets!

Bioslime III Background

Pink Slime, Clear Slime, White Water Mold, Gray Water Mold

What is Bioslime?

The industry’s two largest swimming pool water research labs (Biolab and Baquacil) have spent well into six figures trying to learn how to prevent bioslimes and how to cure them.

First, some background: 

What’s the problem? 

Bioslime is a generic term for various growths that protect themselves from environmental predators by secreting a polysaccharide coating around themselves. The coating feels slippery to the touch – hence the name.  The actual growths may be bacterial or fungal, but we don’t know of any that are actually algal – though our customers always seem to think they are an algae.  In color we’re used to seeing them as white, gray, clear, or pink.

These organisms often grow well in the dark.  They are common in bathrooms (pink slippery stuff along tile grout), in birdbaths, inside oil wells and oil pipelines, and inside medical catheters.

Since the polysaccharide coating protects the actual organism from normal doses of chemicals (including poisons) they are very difficult to kill.

Frankly, swimming pools are much like people. Some are always healthy. Some are sickly. Generally (but not always), people who diet and exercise are healthier than those who do not. Well-maintained pools usually do not catch “diseases” (algae, cloudy water, bioslimes, etc.) However, it can happen to anyone.

Also, there are periods (outbreaks) when some diseases are common (Hong Kong Flu, Asian Flu, etc.) and then they become less so.  It’s the same with swimming pool “diseases”. Some years there’s a lot of mustard algae, or black algae, or cloudy water. After two or three years of problems, they just go away. It’s the ecosystem at work.  We’re hoping that pink slime is following that pattern—and that last year was the worst outbreak we’ll ever see.  However, just in case, we’re still working on a solution.

What Causes it? 

Contaminated equipment (solar cover, vacuum hose, etc.):  Since these spores are part of the environment, any equipment left out and not cleaned may become contaminated.  When the equipment comes into contact with the pool, the spores end up in the water and propagate under the right conditions.

Dirty filter:  A dirty filter is an excellent breeding ground for water mold or other microorganisms because it provides a source of nutrients necessary for growth.  Unlike algae, water mold and bacteria do not need sunlight to make food, so the filter is an ideal location. In some cases, biofilm may coat the hair and lint basket, skimmer and plumbing.

Poor circulation:  water mold or slime is also found behind underwater lights and ladders, or other “dead spots” in the pool.  It will attach itself to an area and remain there until it is physically removed.

Chemical system misuse:  When your three-part system is not followed, the pool becomes vulnerable to a variety of conditions such as water mold and pink slime.         

How do I know if my pool has it? 

If you live in the northern, eastern, or mid-western portions of the United States, you have it. The real question is, do you care?  Roughly 93% of you don’t care. E ither you don’t see it, or you don’t look.  It really doesn’t matter, it’s not bad for you, it’s in your drinking water (normal levels of chlorine do not kill it) and it’s in the air and the rain.

So who does care?  People who do not want to see it growing in their skimmer, inside their ladder, inside their underwater light, etc.  Plus one very important group: people with cloudy water that just won’t clear up.  Unfortunately a really bad case will make the water very cloudy.  Most cloudy water treatments (cleaning the filter, improving circulation, clarifiers, flocs, filter aids, etc.) make only small improvements in these cases.

How do you know that’s your problem?  You don’t.  There’s no test for it.  Even seeing it in the skimmer doesn’t tell us that’s why your water is cloudy – it could be a coincidence. So first, we try all of the normal “cloudy water” cures, because cloudy water is way more common than bioslime.  If they don’t work, then we suspect bioslime.

We also look at how long shock can stay in your pool.  If chlorine shock drops to 3.0 ppm inside of six hours of sunlight, if Softswim C drops to 10 ppm within 2-3 days, or if Baquacil shock levels drop to 30 ppm within 2-3 days, the problem may be bioslime. Remember there’s nothing wrong with readings that low.  Shock is supposed to drop.  It is only the speed of the drop that is interesting.           

What’s the cure? 

Early research indicated that bioslimes were associated with swimming pool water that is low in calcium.  The pink and clear ones seem equally likely to happen in water that has been treated with chlorine, bromine or biguanide.  The white and gray ones seem slightly more common in biguanide pools, but probably because a good number of those pools used simazine algaecides and didn’t use winter kits.  All of the bioslimes seem to be more prevalent in pools that are not shocked often enough, or (for an as-yet unknown reason) shocks don’t last very long in the pool water.  Often, the growths start in the pipes, hoses and filter – the opposite of algae, which always starts in the sunny area of the liner.

To prevent them, we’ve been advising keeping your pool water balanced – especially before it’s closed for winter.  Use a filter cleaner twice a year.  Shock regularly.  Whenever you refill the pool, run 20-30 gallons of water from your garden hose out onto the ground before putting it into the pool. Bioslimes are usually in your drinking water (in small quantities) but they grow very well in a hose sitting in the sun.  Brush the pool often – especially under ladder treads, under the skimmer weir door, and under any folds or flaps in the liner.

Research also indicates an association between high total metal and mineral levels and bioslime growth.  Unfortunately there are many more metals and minerals than we have the ability to test.  Also, several metals at lower levels than we can effectively test could add up their total level to be a problem. (10 x 0.2 ppm = 2.0 ppm).  It would be a good idea to add an additional dose of metal or mineral control product upon opening each year – regardless of any test results that may not indicate such.

All equipment that comes in contact with the pool should be cleaned after use and stored away from the environment.  This will help prevent infection from spreading to the pool.

The filter should be cleaned at least two times per season to destroy any nutrient source available for the water mold.

Check the circulation pattern to be sure the returns are directed toward the bottom and away from the skimmer in a circular flow pattern.

Any leaves, dirt or debris that accumulates in and around the pool, skimmer and hair and lint baskets should be removed as quickly as practical.  This debris provides a nutrient source and a possible breeding ground for water mold.

The pool should be brushed on a weekly basis.  Cleaning should include the steps, behind ladders, underneath slides and diving boards, and the waterline and skimmer areas.

Correctly following your three-part chemical system will minimize the opportunity for water mold or pink slime to appear.

It does appear that bioslimes are a growing environmental disease. They do not hurt anything.  They are not harmful, and town drinking water systems are making no effort to control them.  In fact, one reason for the increase in bioslimes in homes (especially bathrooms) and swimming  pools is that municipalities across the country have been switching to cheaper ammoniated forms of chlorine in their water treatment process. It saves the taxpayer money, it seems to work about as well in killing E-coli and other harmful bacteria, but it does not kill the bioslime in the water pipes as well as the more expensive forms.

The federal EPA would like to enforce safer drinking water (the Clean Water Act), but there is no political will in Washington to pass laws that cost money – and here in New Hampshire, we’d just ignore it anyway.  Live Free or Die!

We have several alternative treatments available to kill an existing problem.  Some are cheap, some are expensive.  The expensive treatments work better than the cheap ones.

 What’s new for Chlorine or Bromine? 

As an industry we have to become more resistant to consumer (that’s you) demands for pools that require no maintenance.  We have all been advising you to give your pool less care than we used to recommend.  Until 1984, we had everyone shocking and algaeciding every week. However, once Baquacil hit the American market with monthly shocking, the chlorine manufacturers started recommending every other week for residential pools (commercial pools still add chemicals much more often than most homeowners).  These recommendations were based on marketing – to reduce the loss of business to Baquacil – rather than on biochemistry.  They were wrong.

Bioguard has come out with new shock treatments for chlorine and bromine based pools. They are designed to be less harsh to the pool than other shocks, and (used as directed) will not raise your chlorine level as high.  Using it at night, you should still be able to swim the next day.  However, unless you want to do some complex testing and calculating (to see if you need to reach a higher breakpoint), we will want to test your water in July or early August just to see if you need to use a more harsh shock once in a while.

It probably isn’t a good idea to use the shocks that contain sodium or potassium monopersulfate on a regular basis – they don’t kill anything, and they give you false chlorine and bromine readings.  We have a special test kit that can fix that, but it’s expensive.

No mater what shock you use, however, we definitely recommend shocking every week.

If you use Bioguard Back-Up Algaecide or Target Non-Foaming Algaecide we prefer that you use half as much, twice as often.  If you use Bioguard Algae-All 60 or Target Non-Metallic Algaecide, use the lower dose weekly instead of the higher dose every ten days.  Ask us to test for your algaecide level (we can do it if you know which algaecide you use) sometime in mid-summer.  Again, July or early August would be an excellent time. 

What’s New for Baquacil or Softswim? 

Bioguard offers Softswim C Test Strips to test your “C” level every week.  If it drops below 40 ppm, re-shock with the normal monthly amount.

They also recommend using  Bioguard Assist tablets every three weeks in your skimmer and pump baskets.  The tablets break down to chlorine dioxide, which is heavier than water, and should travel back to the pool and through your filter system.  The process is a little complicated, and it does chew up some of your Softswim B (it’s not quite compatible), but it has met with some success.

Baquacil has a chemical program called Baquacil CDX that is used to beat back the bioslime, and if you continue on it, keep it from coming back. With the CDX System, you add CDX weekly to help maintain your oxidizer level, and switch to using ¼ of your monthly oxidizer amount weekly (so you do not actually use any more) and watch your oxidizer levels using the 4-way test strips.

Please let us help you, anytime.                                                                                        Revised:  5/20/08


Pool Size: ___________ Gallons Technician: ___________
Date: ________________

We write Pool Tips for the exclusive use of our own local customers. They are meant as a summary of general information, to be discussed in our store, with our staff, to determine which items are best for specific pools. Pool Tips are a trademark of Gull Group, Inc. All rights reserved.

Our suggestions assume that you have given us a proper description of your pool’s size, history and symptoms. Sometimes we can figure it out, sometimes we can’t. Your doctor has years more training, far better diagnostic tools, and makes way more money—and sometimes he or she gets it wrong, too.

  1. Read all labels carefully, and only use chemicals exactly as described on the label. Never mix chemicals together outside of the pool. Some of them can cause a fire or explosion.
  2. Do Not follow any advice or suggestions here without coming into the store, customizing them to your specifics, and receiving them in writing.
  3. Do Not print these out or reproduce for any purpose whatever. They are all copyrighted, and we take our copyrights very seriously.
  4. Don’t Blame Us for anything. It’s free advice, and worth the price paid. We’re trying to help, but pools are complex, and chemicals and electricity are dangerous.
  5. Our Best Advice: Go find a local pool dealer who knows what they are doing, become a steady customer, and give them a chance to learn about you and your pool. Pick a brand, pick a store, and stay with them.