I have never used an algaecide in my new above ground pool and have had no problems to date.   My friends with pools, all seem to use algaecides and chlorine.  Is it a good idea to use algaecide?  Just wondering.

Jeff E., Lakeland, NJ, 8/1/2008

The best way to use an algaecide is to add it before you have a problem!  That way, it can help you avoid a problem.  Chlorine levels rise and fall during the course of the day, depending upon chemical additions and bather usage.  When the sanitizer levels drops too low, algae can begin to grow.   If an algaecide is present, it just might keep the algae under control, until an adequate sanitizer level is restored.  Both above ground and inground pools should use algaecides.  However, the choices may differ because of the materials of construction.  The use of a phosphate eliminator can help reduce the possibility of algae growth, by denying algae a vital nutrient.  This type of product can be used with all sanitizers and with or without a separate algaecide.  Your above ground pool does not have a main drain and means the water circulation is not very good across the bottom.  Consider adding an robotic pool cleaner:  it will act as a roving main drain and help avoid conditions favorable to algae growth.  I hope that I have been of assistance.

Sincerely.  Alan Schuster, 8/1/2008

► Slimy Blobs?

Dear Alan.  My question:  One of my accounts is a saltwater system, when I took the account the owner only had a chemical checking company and no cleaning.  When I arrived to bid the account and look things over, I found that he had this stuff growing on the first step and a few other spots in the pool that looked like blob something or other.  Remember magic rocks how they grew from the bottom of a container, well that's what this looked like but clear and slimy.  Could you tell me what it is ?  And what causes it and how to prevent it from happening again?  I seem to have it under control, still having problems with spots that are not black algae.  Kind of like stains seeping through the plaster.  Owner had a acid wash a few years ago and now stains are appearing.  Thank you so much for your advice, your site is very interesting, I have been reading for the last 2 hours.

Sincerely.  Alan Schuster, 10/1/2003

► All Algae Is Not Created Equal?

A week or so ago, you helped me identify a pool water problem that I had been fighting for several months. You advised me that I should be killing "mustard Algae" (not green algae that I thought was my problem and so did several other local "experts"). Thanks to you and your expertise, and following your instructions I now have a clear, algae free pool. You were absolutely correct, my problem was mustard algae and NOT green algae.  The shock treatment and the sodium bromide made a big difference.  You deserve more than just a thank you, but that is about all I can pass along to you. Thank you!

Bill T., Sun City West, AZ, 9/22/2004

Thanks for the follow-up.  Glad to hear that everything cleared up.  Yellow mustard algae can be a tough one, especially, if you are not familiar with the problem.  So don't be too tough on the "locals."   Enjoy the summer!

Sincerely, Alan Schuster, 9/23/2004

► Phosphate Eliminators  & Algaecides?

Every now and then I get a touch of a greenish water and algae.  Some algaecide and shock, is all that it seems to take.  Is there some advantage to using a phosphate eliminator?  How does it differ from algaecides? 

F. T., Coral Springs, FL, 8/20/2009

Phosphate Eliminators are typically used in conjunction with algaecide and standard swimming pool maintenance.  These products are based on the chemistry of lanthanum:  a rare earth element.  When added to a swimming pool, these lanthanum compounds react with the phosphates and drop their concentration from parts per million to parts per billion.  The presence of phosphates and nitrates can accelerate algae growth and increase the chlorine demand.  Some dealers can perform these tests and it can be worthwhile.  Phosphates are a vital nutrient for all types of algae and their almost total removal from the water interferes with the ability of algae to grow and thrive.  While you can't remove the nitrates in any practical way, eliminating the phosphates can make nitrates less of a problem, by denying algae a vital nutrient.  Literally, the algae starves to death!!!  No algae - no problems with green water.  All this sounds great, but as long as you have people in swimming pools, there will be phosphates added in some quantity.  For this reason the phosphate eliminator has to be added on a periodic basis.  A phosphate test can be performed occasionally to determine the need to add additional product.  As additional assurance against algae growth, it is a good idea to maintain the normal additions of algaecide.  The product is a worthwhile addition to the anti-algae arsenal.  The only downside is that its initial addition will result in a precipitate that has to be removed by filtration and/or vacuuming.   Subsequent product additions are much less of a problem because of the reduced phosphate content of the water.  I hope that I have satisfactorily explained the product.  Enjoy the summer.

Sincerely.  Alan Schuster, 8/20/2009

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► Biofilm?

Hi Alan, your website is very good and I have purchased one of your books.  I have a problem, though, that  I haven't encountered in any of the topics on your site.  I have a rectangular pool; 18' x 36' x 10'deep.  About 34,000 gals.  A week or so ago, I noticed a small mustard algae problem--only several patches.  When I opened the pool this year (I live 40mi. north of the  New Orleans area, and in the winter, all I do is cover it, run the pump 5hr./day, and check for balance every couple of weeks), I didn't add any algaecide.  Being the over-achiever that I am, I figure I'm gonna hit this problem hard and go out and buy a  50% Algaecide .  It's the quat-type algaecide.  After adding the recommended dose for visible algae: 14oz. per 10,000gal, I am horrified!  My water turned milky ,foams when agitated, and has a terrible odor--kinda like mildewed plastic.  I should've just shocked a couple of times, I guess. Here's the scary part; on the walls of the skimmers, I discovered a slimy film (and a lot of it) with the consistency of wet modeling clay, evidently the result of the foaming action taking place inside the skimmer.   AND IT'S NOT WATER SOLUBLE.  What the heck is this stuff doin' to my sand filter?  I shocked the pool right before adding this stuff, and shocked again a couple of days after.  My pool water was like a diamond before I put this stuff in.  I'm ready to go to the chemical people and strangle the first person I see.  Please tell me that the water is gonna clear, the smell is gonna go away, and that the sand in my filter doesn't look like bearing grease.  Thanks for any answer that you can provide.

Jimmy L., Covington, LA, 5/19/2005

If I solve the problem, do I get lunch at K-Paul's.  Just Kidding!  You have several thing which have come together.  During the winter, a biofilm developed.  This is the slimy stuff on the underwater surfaces.  It is comprised of microorganisms that grew in the absence of adequate chlorine levels.  Quats (I hate them) may not kill the biofilm and certainly won't decompose it.  At best, it attaches to the biofilm and impedes its growth.  It also causes unsightly foam.  The water was clear before the quat algaecide was added because the biofilm was on the walls and not in the water.  Adding the algaecide caused the foaming and may have caused some of the biofilm to enter the water.  All you should need to do is add shock and boost the FREE CHLORINE level to 5-10 PPM.  Retest often and add more chlorine, as needed.  Don't drag it out!!!  Once you have established a persistent FREE CHLORINE level, the biofilm should have been destroyed on all of the under water surfaces, including the filter.  Keep an eye on the filter pressure and service accordingly.  You might consider using Zeobrite sand filter replacement media, in place or ordinary sand.  You'll get much better water quality.  During this period keep the filter going 24/7.  Once solved, resume normal pool operation.  I hope that this information proves helpful.

Sincerely.  Alan Schuster, 5/19/2005

► Resistant Algae?

I have a 16,000 above ground pool and I am getting what appears to be black or dark brownish gold mustard algae in the ends of my pool, more prevalent in the shallow ends of the pool.  The deeper section is in the middle and seems less likely to be affected.  I have a DE filter (running about 8 hours and the cleaner runs 3 hours) and the problem seems to have begun when the water temperature reached 69 degrees.  I have shocked the hell out of the pool and when I sprinkle the granular shock on the deposits it clears up for a day and then begins reappearing.  I tried treating with black out, and then with some yellow algae treatment.  The yellow required I raise the pH to 8.0 and treat and shock and treat and shock 12 hours later and then shock only again 12 more hours later.  That is where I am now, but I don't want to shock again as the pool smells like a bottle of laundry bleach now.  There is 4-5 ppm of chlorine, same level of free chlorine.  I am thinking after reading your FAQ's that if I have algae growing in my pool of chlorine.  Maybe it is metal deposits precipitating out of the water.  The black stuff also is not affected at all by brushing until I shock the hell out of the pool and then most of it disappears for a day or so, but no longer.  Any little bit left easily brushes away, but most disperses on its own.  I am taking a sample in tomorrow to get the metal contents tested and see if this confirms what I think I read in your FAQ's.  In the meantime, if you have any other ideas I am interested in hearing from some knowledgeable parties.  I am getting sick and tired of buying anywhere from $40-$100 worth of chemicals that only fixes the problem in most cases for 12 hours.  The 16 year old pool experts and the little bit older store managers don't seem to be cutting it for me so far.  Anxious in Austin TX

John B. Austin, TX, 4/10/2003

If it turns out that you have a heavy metal problem, it would be in addition to an algae problem.  What you are describing does not seem like the classical case of mustard algae.  The algae treatments that you have added, probably contain an ammonium salt.  This would account for the odorous conditions that you have described.  The ammonium salt reacts with the chlorine to form chloramines, an odorous form of combined chlorine.  It has been demonstrated the high levels of chloramines can be effective against certain types of algae.  After the algae has been destroyed, it is mandatory to shock the pool with large amounts of chlorine in order to destroy the chloramines.  In your case, in would appear that algae is somewhat resistant and is not responding to this chloramine treatment.  I suggest that you treat this problem on the basis of being a resistant algae.  Lower the pH to 7.0.-7.2.  This will help make the  chlorine more effective.  Add chlorine shock, at the rate of 2 pounds per 5,000 gallons, until a Free Chlorine level of 5-10 PPM is achieved and persists for an overnight period.  It may be necessary to add more shock or make further pH adjustments, because of the prior addition of the other products.  The longer this takes, the more the filter continuously.  Redirect the return flow to send more water into the affected areas.  The simple installation of a circulation booster can help make algae growth less likely, by improving the chemical distribution and eliminating dead spots.  For information on "The Circulator" please click here. The addition of a polymer algaecide will further assist in controlling the algae.  Brush the effected areas to help the chemicals reach the algae growths.  If you have an automatic pool vacuum, it will be helpful in getting the chemicals to reach the algae.  After the problem has been eliminated, resume normal filtration and chlorination and restore proper pool water chemistry.  The practice of sprinkling granular chlorine, directly on the effected areas, is not recommended and could result in damage to the vinyl liner.  I hope that this information will prove helpful.  Good luck.

Sincerely.  Alan Schuster, 4/10/2003

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I had a new liner, cartridge filter, and an ionizer installed this spring in my in ground pool.  The pool is about 22,000 gal.  I have a problem with slime on the bottom and sides of the pool.  It appears clear, but it makes the pool very slippery and unpleasant.  I have tried increasing the level of the ionizer and I have tried decreasing it.  It currently reads between .2 and .3 on the copper ion tester.  I have tried to use non chlorine shock and it helps some, but the slime is back in 2-3 days.  The pool installer and pool stores around here are no help.  Yesterday, I did the shock again and then put in an algae preventer liquid.  Today, it still has a little of that slime feel to it.  What is wrong?  How do I get rid of it? The summer is "slipping" away and my pool is getting unusable.  Thank you for your help.

Nameless, 8/4/2005

The slime is a most likely a bacterial film.  Copper is recognized as an algaecide and not as a bactericide.  I would add chlorine and boost the Free Chlorine to 5-10 PPM.  It will kill and decompose the slime.  Dealers that sell ionizers may be reluctant to suggest chlorine, as that was part of the reason to buy the ionizer.  There is no reason that you can't use chlorine to maintain a 1-2 PPM level:  both to oxidize wastes and to act as a sanitizer backup.  The presence of the ionizer will allow you to do this with less chlorine product.  The recurring nature, of the problem, could be indicative of dead zones and poor circulation.  The 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.  This information should help get you back in the swim.

► Algae Hideout?

Hi Alan, when I had a swimming pool it used to suffer badly from Algae build up.  It did not matter what I did I could not get rid of it until one day the pool light blew.  On removal I found a pocket of algae that was the breeding ground.  Being behind the light it was never in the moving water and therefore did not get treated.  I hope that this knowledge might help some of the visitors to your site who are experiencing algae problems.  Regards.