Pink Pool Algae-Mold Problems

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"Pink" algae or slime may be pinkish in color, but it is not an algae. The problem is actually bacterial in nature. The best algaecides to use for this problem are either Polymer Algaecides or Silver Algaecides. These products exhibit some antibacterial properties: other algaecide such as "quats" or copper are not effective against these bacterial problems. Another effective treatment is the use of a Sodium Bromide product. However, the use of sodium bromide, in a chlorine pool, can increase chlorine usage, for an indeterminate length of time. Either course of treatment must involve superchlorination, in order to kill and decompose the bacterial growth. This type of problem can recur, if the conditions and water chemistry are hospitable. When pink algae, mold or slime issues, occurs in a biguanide-sanitized pool, on a recurring basis, it is a sure sign of the development of a sanitizer-resistant microorganism. The sensible solution is to stop using biguanide and permanently switch to another type of sanitizer.  In addition to proper sanitation, good circulation is a must to help prevent algae growth in areas with stagnant water or dead zones.  The use of The Circulator, as a replacement for standard return jet fittings, can dramatically improve circulation, better distributing sanitizer to all areas of the pool.  Should problems arise, refer to the Pool Problems Page, as a source of problem-solving information, broken down into various categories.  Scroll down the page and click on the linked keywords, catch phrases or images, in the archived answers below, to access additional information, on that topic or product.

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► Pink Algae?

There is some pink, slimy looking, slippery-feeling, growth in the hopper end of the pool - vinyl, built-in, chlorine maintained, 20000 gallons, heated and not looking so great. If it wasn't for the color, I'd think that it was algae. What do you think and how do I handle it?

Martin A., Terre Haute, IN, 6/23/2018

What you think might be "pink" algae is really not algae at all. It is a bacterial slime problem and can be controlled. Make sure that your pH is 7.0-7.2, in order to make the chlorine more effective. Add a quick acting shock at the rate of 2 pounds per 5000 gallons, in order to boost the Free Chlorine Test reading to 5-10 PPM. Use a Free Chlorine Test Kit - this is important! Operate the filter continuously and try to maximize circulation in the deep end. Retest the Free Chlorine every few hours and add more shock, as might be necessary. Brush any areas with deposits. Add either a Silver or Polymer Formula Algaecide: these products have effectiveness against many types of algae and bacteria. As an alternative to these algaecides, or even in addition, add one of those "Yellow" Sodium Bromide Products. This will generate bromine in the water, which is especially effective against "pink" algae or slime. If after an overnight period, the Free Chlorine level is at 1-3 PPM, marked improvement should be seen. If the water is cloudy, it is likely from dead algae and organic debris: use a liquid clarifier to help remove these materials.  Once sodium bromide is added chlorine usage will increase for some indeterminate length of time.  However, if it solves the problem, it is worth doing.  Restore the pH to optimum and resume normal filtration and chlorination. I hope that I have been of assistance.

Sincerely. Alan Schuster, 6/23/2018


► Pink Staining On Liner Track?

I opened my pool yesterday to discover pink stains on the top band of the liner. It is only on the one inch white strip where the liner is attached to the wall track, well above the water level. From other articles on the web, it appears to be an algae, but no reference is made as to how I get rid of the stain. Any suggestions would be appreciated.

Randy M., Nova Scotia, Canada, 4/30/2012

It would seem to be some type of microorganism that developed, not in the water, but in the condensed moisture that formed on the track that holds the liner in place. As the springtime weather improved, the winter cover allowed the side wall area, directly under it, to become moist and warm. This, in turn, permitted this microorganism to grow. You should be able to use a scrub brush and an solution of 1 part algaecide and 3 parts water, to remove the stain. Once the pool water level has been restored and the water quality optimized, the chlorine in the water should destroy any remaining stains, by sponging water onto the effected areas. I hope that this information will prove helpful.

Sincerely. Alan Schuster, 4/30/2012


► Pink Slimy Stuff?

After finding pink slimy stuff in my swimming pool, I called the pool company which installed my pool and they told me that I should use a copper based algaecide. I tried to find the copper based algaecide locally but to no avail.  I called another pool company which is closer than the company who installed my pool and they told me to bring in a water sample and they could help me treat my problem. They gave me granular trichlor and told me to shut off my pump and to brush my pool and let it sit over night and then vacuum to waste. Then to clean my filter. I will do that today but I am concerned that not all of my pink areas have disappeared even after I have scrubbed and scrubbed on them. I have a 35,000 gallon inground gunite pool. I see that you recommend treating it with Silver or Polymer Formula Algaecide. How do you know if an algaecide is one of those? Is it the active ingredient? Have I just wasted $60, if my problem is not solved, did I get wrong information? Sincerely.

Michele in Missouri, 5/18/2014

Copper would not be my recommendation, as you have already discovered. The "pink" algae is a bacterium and copper algaecides are not bactericidal. Polymer and silver algaecides are much more effective against this problem. Yes, you will have to read the ingredient statement on the label to make sure that you are adding the correct type of product! Another good method is to add a "Yellow" sodium bromide product and shock the pool. This will create bromine in the pool and that has been shown to be effective against this type of pink slime problem. Add enough shock to raise the Free Chlorine reading to 5-10 PPM and keep it there until improvement is seen: usually 1-2 days. The granular Trichlor will only work on local areas and is not a good way to treat an overall condition. I don't know if the condition is overall or limited to spots, so I can't comment on the appropriateness of the product. However, improving the water circulation will aid in the distribution of chemicals and that can help prevent and solve many problems.  The Pool Circulator is an easy-to-install accessory that can boost circulation, in a very dramatic.  I hope that I have been helpful. Good luck.

Sincerely. Alan Schuster, 5/19/2014


► Pink Water Mold?

I have been using biguanide for a few years and have developed a problem with something being called "water mold." It has a pink look to it. I shocked it a few times with peroxide. It got somewhat better, but is still there. I have heard that this can be an ongoing thing. What's the story? Thanks.

Paul B., Marlboro, NJ, 8/3/2009

From your description, it sounds like you are experiencing a problem that is not uncommon amongst biguanide users. Water mold is caused by a microorganism that has, unfortunately, become resistant to the biguanide. In order to treat the problem, chemicals such as chlorine shock or non-chlorine shock, have to be added to the water until a Free Chlorine level of 5-10 PPM is achieved. It is important to perform the Free Chlorine Test. The water will go through various green-brown-cloudy stages, until finally the water clears up. It takes a lot of shock, at least 2 pounds per 5000 gallons, in order to start the treatment. If after application of the shock, a Free Chlorine reading of at least 3 PPM is not reached, it will be necessary to add additional shock product. The shock will destroy all of the biguanide and there must be an excess, in order to destroy the water mold. A consequence, of adding the shock, is the destruction of all of the biguanide. Resuming maintenance on biguanide will require that you start from scratch. To resume on biguanide, you must neutralize all of the chlorine remaining in the pool. A chlorine neutralizer product is available for this purpose. Once a biguanide-resistant microorganism has developed, there is no guarantee that it will not return, even after successful treatment. For this reason, you might consider an alternative sanitizer: chlorine, bromine, salt Chlorine generators, ultraviolet sterilizers, ozone generators, ionization or a combination. Otherwise, you just might get the problem back, in spite of your best efforts. I hope that I have been helpful. Good luck.

Sincerely. Alan Schuster, 8/3/2009

► Pink Mold?

I found pink mold in my pool as I was closing it for winter. I plan to get rid of it when I open the pool in the Spring (I hope), but I'm wondering if this is harmful to people who swim in the pool? I also want to thank you for your web site. It was very helpful to me on how to get rid of this Pink Mold. Thank you.

Tom I., 10/9/2008

Pink mold is a bacterial problem and is probably the result or poor sanitizing practices and/or poor circulation. The Circulator is the easy to improve circulation and eliminate those dead zones, that promote algae growth.  It can be somewhat resistant to sanitizers, especially biguanide. I suggest that you treat with a shock treatment, upon opening. While this particular bacterium might be benign, the presence of obvious microorganism growths does indicate the possibility of inadequate sanitation. You might consider a switch to a Salt Chlorine Generator.  It is the better way to do chlorine, providing more control, better results and no more chlorine to measure. handle or store. Good luck next spring and thanks for the kind words.

Sincerely. Alan Schuster, 10/9/2008


► Pink Bacteria?

I've had pink bacteria for a couple of years. I've super-chlorinated, it comes back. I added an ammonium sulfate product last year - it was still there when I took off the winter cover. I super-chlorinated. & added the product again. Thought things where going ok, but my readings are way off - total chlorine ok at 3 but free chlorine ~10, hardness ~1000, stabilizer ~150 (dipstick reading).  Lots of birds pooping in the water, but afraid to shock any more. I took the stabilized tablets out of the skimmer, took off the pool cover, increased the heater temp. pH ok ~7.5, total alkalinity ~150. pool high right now (rain) ~45,000 gallons, 20x40.  Any thoughts?

Margaret, 5/28/2016

Ammonium sulfate and is used primarily to boost the combined chlorine readings, which in turn seems effective against certain problems. Given your lack of success, I suggest that you try something else. Try adding a sodium bromide product. This product will convert the chlorine, both free and combined into bromine sanitizer. Bromine seems to much better than chlorine, in controlling the pink bacteria problem. To start off with a level playing field, after the sodium bromide is added, add shock, as necessary, to boost the Free Chlorine level to 5-10 PPM. Test the level, every few hours, and add more shock, if required. Once the Free Chlorine has stabilized, the problem should be gone. Thereafter, maintain normal pool chemistry. The recurring nature, of the problem, could be indicative of dead zones and poor circulation. The Pool Circulator is a circulation booster insert, that dramatically eliminates dead zones and makes the water come alive. You'll get better distribution of sanitizers and that should help minimize algae and other related problems. I hope that the information proves to be helpful.

Sincerely. Alan Schuster, 5/28/2016


► Pink Algae And Poor Choices?

Is it possible to have pink bacteria in a pool with a salt system installed? If so what is the best way to get rid of it? We have used an algaecide that contains 3.3% copper and 96.7% other ingredients. It contains polymeric polyacrylate and gluconate stabilizing agents. Is this considered a polymer algaecide?  I think it would be beneficial to drain a portion of the pool, especially, if the cyanuric acid levels are too high. I do have a test strip reader and I have not been happy with the inconsistency of the results.

Jeff S., 5/16/2008

"Pink" algae is a microorganism that might be somewhat resistant to chlorine, as opposed to an algae problem. Salt chlorine generators tends to make the pH rise and, if not corrected, this makes chlorine less effective. Adding a polymer algaecide is also a good idea. The pink problem could have been made worse by high pH and high cyanuric acid levels. That is a copper algaecide and is a poor choice for this problem. Copper is an effective algaecide, but "pink" algae is actually a bacterial problem. A polymer algaecide contains a chemical with the term (dimethyl iminio) repeating several times. It is a much better choice, for this problem.  Keep the pH closer to 7.2 and the free chlorine at the high side of 1-3 PPM. Test strips give suitably accurate results, with great convenience. They are not exact! Adding a strip reader does not make it more exact and can add another layer of complexity and error. A better water testing choice would be the ColorQ Water Analyzer. It is all digital, eliminating color-matching and guesswork. If the cyanuric acid level is too high, over 100-150 PPM, replacing some water will make the chlorine, at any given level, more effective. Don't forget to test the salt level, after the water replacement, and make the necessary salt addition. I hope that this information proves to be helpful.

Sincerely. Alan Schuster, 5/16/2008


► Purple Slime?

Dear Alan, the other day when took out my pool cleaner I noticed a purplish slime on the hoses. When I rubbed my finger across it, the purple residue just wiped off easily. I looked over the entire pool, and there doesn't seem to be any of it anywhere else. I did have an outbreak last summer of pink algae, but I used your suggestion of sodium bromide, and it took care of the problem. What do you think this might be? Sincerely.

Ken M., 2/21/2020

It is probably some type of microorganism. The fact that it is not present, in the pool, should mean that it is not chlorine-resistant. In the future, if you see something like that, soak the parts in a large container or barrel with some water and chlorine. While it is not a guarantee that it won't get into the pool, it is a good practice, especially after a problem situation. The best defense against microorganisms is proper testing and sanitation. The two do go hand in hand. No matter how a pool is being sanitized, there is a ColorQ 2X All-Digital Tester that will do the job. Glad to hear the advice worked. Enjoy the season.

Sincerely. Alan Schuster, 2/21/2020


► Bye-Bye Pink Slime?

I let the FC in my salt-water pool fall to 0.2 for about a day a couple weeks back which resulted in cloudy water. Using extra chlorine and blue clarifier, it cleared up nicely. Well now, about a week later I find this pink, slimy stuff. Well now I’m an expert on that, too. I’ve just set the chlorinator for 100% and plan to shock the living, holy $*#@ out of it. I think I’m going to go for 10 ppm. Then let the sun bake it back down to 5 where I’ll leave it for a few days. In the meantime the filter will be running non-stop. I’ve got a pool party planned for 2 weeks from now, so I don’t want to mess around. My research has indicated that a high chlorine dose is the best way to go, especially for someone who makes it, right in his pool. Anything that has been in the pool, such as my brush should also reside in there during the shocking. One other thing I found was to backwash the filter when it’s all said and done to get rid of the stuff and one person suggested changing the media. Early backwashing goes against what you and I have discussed as far as filtration quality is concerned, but in this case, I think I like the idea of sending that gunk down the line. But what about media replacement? Is that overkill? Mine’s only about a year old. Thanks again, Alan.

Kendall, 8/7/2006

When you recirculate water with 10 PPM of free chlorine, you pretty much sanitize the filter as well. Backwashing reduces the filter efficiency. However, if the pool is a swamp, it helps get rid of loads of chlorine-consuming gunk. Your pool is not a swamp and I would backwash only when the pressure is too high. For better results and a reduced need to backwash, replace the sand with zeolite a sand filter replacement media. It works even better with a salt chlorine generator. Adding brushes to the pool can't hurt. But, I am not sure it really solves anything. You can't sterilize the environment and algae is really always there: just waiting for the right moment to bloom. I hope that this information is helpful.

Sincerely. Alan Schuster, 8/7/2006

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