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topic 9128

Copper Sulphate as Swimming Pool Algae Remedy?

A discussion started in 2001 but continuing through 2019


Q. I'm hoping someone can help me with this question, and I know absolutely nothing about copper sulfate [paid link to product info at Amazon].

My question is this: we own an in-ground swimming pool, and last year had terrible problems with algae because of heavy rains all season. We spend hundreds of dollars (as did many other people) in trying to control the problem. Of course my husband thinks that we didn't need to spend all that money through the swimming pool experts and that much of their chemicals are just a money making scam. My husband had also been told by a friend, that copper sulphate was the answer to this kind of problem. After using a very small amount of it in his pool, it apparently cleared up this friends nasty swimming pool algae in no time. It was also pocket-book friendly. This friend claimed that he received this information as a tip from a someone who works for a swimming pool company, and that this remedy is not sold as a water cleaner/clarifier by swimming pool companies.

My query lies in wondering why this is not sold by swimming pool companies as a water clarifier/cleaner. Is there a reason for this? What would be the long term effects/damage or heath concerns involved in trying something like this? Is copper sulphate an agent that is already used in manufactured swimming pool chemicals? My husband wants to try it this year, but I'm a little nervous about it. I could easily go and ask the swimming pool people about it, but I wanted an unbiased and educated opinion on this subject.

I'd appreciate any input on this.

Thank you,

Tracie K. Wren
- Cobden, Ontario, Canada


A. I occasionally use copper sulfate (we use "f" instead of "ph" in the states, eh?) in my pool. Municipalities have been using it for years to control algae growth in surface drinking water supplies. Copper sulfate is not a substitute for chlorine or other purifying media. It is, essentially, a metallic poison that in small concentrations inhibits algae growth. I use it in 1-2 mg/liter (as copper sulfate) concentrations. You should have access to a source to analyze trace copper should you need to add more. Like I said, copper sulfate is poisonous, so use it at your own risk.

George Brackett III
- Utica, New York


Q. Copper Sulfate has been used for years as an effective means of algae control in surface water but is it safe to use in swimming pools and if so how much would you use in a 30,000 gal pool and how often...

Thanks for any help.

Bobby Lee
Hobbyist - Russellville, Alabama

InstaTest Cu/pH/Alkalinity


A. One part per million of copper in drinking water is quite safe, and 0.5 parts per million is enough to control green algae in swimming pools. Most copper sulphate contains around 20-25% copper,so a 50,000 liter pool would require 100 - 120 grams copper sulphate if the pool is green I would give a once off double dose. Test kits are available to test the concentration off copper in the water. A word of caution, copper used in conjunction with too much chlorine will eventually cause black stains on marble plaster, although these can easily be removed by "acid washing" the pool. One cup of calcium hypochlorite per week will be enough to keep the water sanitised. As always maintain a pH of 7.2 - 7.6

Garry Sunderland
- South Africa

Pool Shock


Q. I have exactly the same problem with the chlorine and the sulphate turning the grouting black, can you please tell me what "One cup of calcium hypochlorite per week will be enough to keep the water sanitised." does this get rid of the black or do I have to empty the pool and use acid, what is another name for calcium hypochlorite and where would I be able to buy it.


Robin Dillon
- Minorca, Spain


A. Another name for calcium hypochlorite is probably 'chlorine tablets'. So, no, these don't remove the black stain, excessive use of them causes the stain.

Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha


A. Calcium Hypochlorite is also known as unstabilised chlorine , i.e., it is not combined with cyanuric acid. It comes in granular or tablet form. Stabilised chlorine, e.g.(Trichlorisocyanuricacid)is usually in tablet form in those floating chlorinators . Both are chlorine and will stain marble plaster black when used with copper.

Copper sulphate, whilst being an excellent algaecide will not sanitise (disinfect) your pool water; that's where the chlorine comes in, or you could use hydrogen peroxide [paid link to product info at Amazon] it will sanitise the water and won't stain the pool,it has the added benefit of being harmless to the ozone layer (it breaks down into hydrogen and oxygen). Draining the pool and washing down with a weak hydrochloric acid solution will remove the stains. Ask the guys at the pool shop how to do it, so you don't damage your plaster.

Garry Sunderland
- South Africa


Q. I have had a pool for 4 years and use an ioniser as the primary water treatment with occasional chlorine treatments. I noticed that the grouting in the tiles has turned bright green and also the children's scalps and hair have turned green! Obviously I am worried about this, On testing the water I found high levels of copper how can I remove it from the water?

Mrs L Aquilina
pool owner - Gharb, Gozo, Malta


A. A chelating agent will remove the copper from the water (ask at the pool shop) As for the hair, a little vinegar in the final rinse after washing should remove the green tint.

Garry Sunderland
- South Africa


Q. I've been thinking about using copper sulfate in my vinyl lined pool. I've been searching the web a long time to find out the difference between copper sulfate and the ionized copper that comes from the ionizers that's being sold. If I'm correct their both positive ions, one is water soluble, and the other just(for lack of the proper word) invisibly hangs in the water. Does anyone know the difference? This is the first site I've come across where someone has actually said they use copper sulfate in their pool. Thank you.

Ruby Edwards
- Morganton, North Carolina, USA

May 7, 2012

Q. This is a follow-up question. Use of copper sulfate in swimming pool to control algae, is this a one-time treatment or weekly or monthly treatment? Or just add some when sign of algae appears?

john hu
- baton rouge, Louisiana

June 25, 2013

A. I have been using copper sulfate in my above-ground (11,000) gals. At a rate of 4 TEASPOONS of the Granular dissolved in 4 gals of water then poured evenly around entire perimeter of the pool. I do this once a month. Additionally, I add one lb. of granular Shock about once every 6 to 10 days, depending on traffic and rain. I have been doing this for 4 years and have the bluest cleanest pool around. The amounts I use were prescribed to me by an engineer who works for a chemical company that sells to municipalities all over the SE U.S.
Naturally you are not going to get any information about this from your pool supply companies. I pay $25.00 for 5 lbs. of Copper Sulfate, which is about a 6 to 8 year supply.

Randall Gatlin
- Gulfport, Mississippi USA

February 6, 2015

Q. OMW, 9 years later, thank you -- so should I add the copper sulphate solution at night or in the day?

sheryl paul
- johannesburg, south africa

February 2015

Hi Sheryl. You're less likely to stumble on something and hit your head and drown in the daytime; and more likely to encounter a skunk or porcupine or other nocturnal animal at night :-)

Actually, to my knowledge, there is no particular difference ... but we'll see if someone calls me out as wrong.


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

February 12, 2015

!! During the past twenty years or so I have used an electronic copper ion generator .... two electrodes into my filter unit ... which operates with the filter timing sequence. Before that I used Copper Sulphate. Very inexpensive and effective in my 80,000 liter pool. Be very careful when you put in any pool chemicals. READ the labels and understand what they mean. We have pool companies that will sell you acid at 4x the price by calling it 'Pool Sparkle'. Everything is poisonous ... in excess (there are even toxic relationships). Do your homework. Ozone or UV are sanitizing options to replace chlorine but algae control is not part of that protocol ... except that chlorine will kill or bleach algae. I have found that a neutral pH is the first parameter to control.

Hans Ruysenaar
Retired - Johannesburg, Gauteng South Africa

20 Mule Team Borax

April 11, 2015

A. I have been using copper sulfate for many years now at the .5 PPM ratio, and of course chlorine, as a sanitizing agent. There is a trick to using this which I have yet to see posted and that is to also add 1 lb. of powdered Borax /10,000 gallons of pool water. The borax removes oxygen from the water and ties it up as H2O2 ( hydrogen peroxide ) in the pool water, this is degraded daily by sunlight, it is harmless to you at this dilution, it will prevent algae ever becoming established when combined with chlorine and copper sulfate, it will also kill out established black algae in the pool.

Thomas Moore
- Adjuntas Puerto Rico USA

April 19, 2015

Q. I have heard that Borax is good to use for water clarity but I hesitate, not knowing about the frequency or how to test its level of intensity. Is there any information about those factors that may be helpful?

Larry Dumm
- Roseville, California USA

Copper, alkalinity & pH Test Strips

May 20, 2015

A. A few years back there were claims all over the internet about borax being the ultimate pool treatment. I tried it.

As best I could tell, even in fairly large quantities it did nothing at all.

A tiny bit of copper, 1 ppm or so, is the trick to control algae. I happen to use copper napthenate because I have some, but copper sulfate is fine.

You can buy a copper test kit for a few dollars on eBay, or you can add just a tiny bit (as in the above responses) a few times each season.

Of course you must still control pH at 7.2 - 7.4 or thereabouts, and you need chlorine to be certain there are no pathogens or other harmful microbes.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

May 22, 2015

A. Believe it or not, in the European Union Borax and Boric Acid are SVHC's.

Tom Rochester
Plating Systems & Technologies, Inc.  
supporting advertiser
Jackson, Michigan, USA
plating systems & technologies banner ad

June 21, 2015

Q. My daughter is allergic to copper sulfate. Will it harm her in the pool?

eileen dewar
- lachute que. canada

July 2015

? Hi Eileen. Sorry but I don't even quite know what that means. I would think that everyone is "allergic" to copper sulphate -- it's a poison. But many ponds and medium sized lakes are dosed with copper sulphate. What (if anything) does her doctor or dermatologist say about her condition and this situation?


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

June 28, 2015

Q. to Randall G
- Gulfport, Mississippi or anyone willing to answer.

Randall, you say you purchase Copper Sulfate for your pool, what company would you recommend? Also, in the pool industry there is a company named "[supplier name deleted by editor]" that makes a fortune off of this stuff, their primary ingredient is Copper Sulphate Pentahydrate (Chelated) is this the same thing you use? Please advise, Thanks.

Bobby Grant
Pool Business - Anna, Texas USA

June 2015

thumbs up signHi Bobby. Randall's posting was from over 2 years ago, so we don't know if he'll reply -- we'll see. But we can't discuss what ingredients particular suppliers use in their trade-secret products in this public forum -- that comes too close to trying to crowd-source industrial espionage :-)


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Striving to live Aloha

Copper Sulfate in swimming pool is rusting the heater

July 11, 2015

Q. I used copper sulphate as opposed to chlorine as an inexpensive and effective way to treat my swimming pool. I used it for 10-15 years. Three years ago, I purchased a water heater for the first time. Within 3 months the heat exchanger was all rusted out. I stopped immediately using copper sulphate and went for a whole summer using just chlorine. I started the pool up this spring and observed a leak. I checked the heater and the heat exchanger was starting to rust. My question: how long is will it take for the copper sulphate to be eliminated from my pool and is there some thing that I can use to quickly nullify the rusting effects

James Campbell
- Niagara Falls, ON, Canada

July 13, 2015

A. Many metals corrode. Only iron alloys, i.e., steel, rust.

Your pool heater "rusted out"? That makes no sense. Most pools use chlorine which, by itself will cause rapid rusting of plain steel. Copper may accelerate rusting of steel.

The bottom line is, in my opinion, steel is completely inappropriate for heat exchangers which have contact with swimming pool water.

If you were sold a steel heat exchanger for swimming pool use, you have a valid complaint with the manufacturer.

If it is a gas fired unit, the heat exchanger parts which contact pool water should be copper or a chloride resistant stainless steel alloy like 316. I used a copper/solar heater for many years with zero leaks.

If a low pressure solar heater, then plastics like PVC or polypropylene can be also used.

Steel? No. No way.

But, if you still want to get the copper out, dump and replace the water.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

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