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copper sulphate as Swimming Pool Algae Remedy?

Q. How much copper sulphate [on eBay or Amazon (adv.)]do I add to a 50,000 gallon pool?

Thomas Donald
- Long Island New York
July 13, 2022

A. Hi Thomas. There are some very insightful answers on this page; I personally really like the ones from Garry Sunderland and Randall Gatlin. But you'll have to do some arithmetic to scale up from their suggestions.

Luck & Regards,

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

⇩ Related postings, oldest first ⇩

Q. I'm hoping someone can help me with this question, and I know absolutely nothing about copper sulphate.

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 sulphate(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 sulphate 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 sulphate) concentrations. You should have access to a source to analyze trace copper should you need to add more. Like I said, copper sulphate is poisonous, so use it at your own risk.

George Brackett III
- Utica, New York

A. Hi Tracie.
The reason sellers do not tell you about copper sulphate is as clear as the pools that have copper sulphate in them (including mine): it would crush their income.
A large % of their income comes through repeat selling chlorine to customers.
I added two cupfuls to my pool two years ago and it has been clean ever since - Crystal clear in winter.

Bruce Russell
- New Zealand
October 13, 2022

InstaTest Cu/pH/Alkalinity

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Q. copper sulphate 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

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 of 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

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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 can cause the stain.

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

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 [on eBay or Amazon (adv.)] 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 bulk on eBay or Amazon (adv.)] in the final rinse after washing should remove the green tint.

Garry Sunderland
- South Africa

Q. I've been thinking about using copper sulphate in my vinyl lined pool. I've been searching the web a long time to find out the difference between copper sulphate 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 sulphate in their pool. Thank you.

Ruby Edwards
- Morganton, North Carolina, USA

Q. This is a follow-up question. Use of copper sulphate 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
May 7, 2012

A. I have been using copper sulphate 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 sulphate, which is about a 6 to 8 year supply.

Randall Gatlin
- Gulfport, Mississippi USA
June 25, 2013

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 6, 2015

A. Hi Sheryl. To my knowledge, there is no particular difference ... but we'll see if someone calls me out as wrong.

Assuming they don't, I'd say you're less likely to stumble on something and hit your head and drown in the daytime or encounter a skunk or porcupine or other nocturnal animal :-)


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

A. 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
February 12, 2015

20 Mule Team Borax

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A. I have been using copper sulphate 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. 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 sulphate, it will also kill out established black algae in the pool.

Thomas Moore
- Adjuntas Puerto Rico USA

A. Hello guys, let me share my experiences ... I have a 18000 gallon in-ground liner pool. It is equipped with a sand filter and a post filtration cartridge filter plus a homemade copper ionizer. I actually add copper sulphate to maintain .300 ppm limit. Add one pound and check the copper concentration with a copper concentration kit. Have not had any problems ever !
When I see spots of brown algae, I drop shock granules where the algae spot is, using a PVC tube, and it is gone in minutes !

User - Benton [Louisiana]
August 3, 2021

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
April 19, 2015

Copper, alkalinity & pH Test Strips

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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 sulphate is fine.

You can buy a copper test kit for a few dollars ⇨
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

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

Tom Rochester
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.
supporting advertiser
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Q. My daughter is allergic to copper sulphate. Will it harm her in the pool?

eileen dewar
- lachute que. canada
June 21, 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
Striving to live Aloha - Pine Beach, New Jersey

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

Randall, you say you purchase copper sulphate 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 28, 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 (beyond what is revealed on the SDS) -- that comes too close to trying to crowd-source industrial espionage :-)


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

copper sulphate in swimming pool is rusting the heater

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 11, 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

Q. Great information on thread - so thanks! My 100,000 Litre cement pool is extremely green, including along the sides. I added about 2-kg of 'shock' 48-hrs ago and it is still very green... and cloudy. Based on a post above it appears I will require 400 grams of copper sulphate based on 100 grams per 50,000L plus a 'one-time-double-dose'.

I would like to know the most effective way to add this to my 20x40 pool!
e.g., should I mix with water first, (how much water) and pour around perimeter, or is it okay to pour into skimmer filter. And also, how long should the filter run to move solution around enough to work effectively?

I also read on another site that copper sulphate can leave purple stains.... is this a probable risk with using 400 grams in 100,000 L pool?

Thank you!! LA

Lori-Ann Gill
- London, ON Canada
July 17, 2015

Q. We are first time above ground pool owners. I've been doing a lot of reading about using copper to control algae and sanitize the water. My question is do I use it in conjunction with chlorine? And what's the best way to figure out how much I should be using? I have a smaller maybe 5000 gal pool at most. Thank You.

Jennifer Kasper
- Johnsburg, Illinois, USA
July 24, 2015

RFQ: Does anyone out there know of a company that can identify algae? We have tried many products in our huge (85,000 gallon) concrete swimming pond which is filtered through 2 gravel/plant filled bogs. We'd like to know what type of algae we are trying to treat.

Sarah Lazard
- Penn Valley California
August 22, 2015

Ed. note: Sorry, this RFQ is old & outdated, so contact info is no longer available. However, if you feel that something technical should be said in reply, please post it; no public commercial suggestions please ( huh? why?)

A. Algae needs 5 things to live: water, sunlight, carbon dioxide, nitrates, and phosphates. Take away any one, and it will die. Phosphate remover, though expensive, is very effective. BTW, phosphates come primarily from pee in the pool water. Don't pee in the pool, and algae control becomes much easier.

I am a pool pro. I used to use copper sulphate pentahydrate, but discontinued it. I was getting green hair complaints from my customers. You also risk having an unsightly purple precipitate from the copper with pH changes.

Carl Stephens
- Central Florida, USA

Q. Thinking of trying copper sulphate in my 24' round above ground pool. I know this is going to display my total ignorance of pool maintenance, but do you pour the solution around the perimeter of the pool with the pump on filter, recirculate, or turned off? Please don't laugh, my husband took care of all this, and I'm a rank beginner!!

Kathy Rector
- Leesville, Louisiana
August 25, 2015

A. Hi Kathy. I think what's best is good mixing. Pouring it around the edge, maybe stirring a bit with a paddle, while the filter is on is probably fine. But it would be better to pour it into a watering can and dilute it first. Usually, the product will suggest a whole regimen though (i.e., how it best fits into the sequence of chlorinating, shocking, pH adjustment, etc.)


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

Q. How long should we wait to swim after adding the copper sulphate? I have a 24 ft above ground pool.

Christie Miller
- Houma, Louisiana
August 25, 2015

Q. Can I use copper sulphate in a vinyl lined in ground pool? If so, how much do I use for 22,000 gallons?

Melanie Quim
- Anderson, Indiana USA
August 25, 2015

Q. I saw a post of Facebook saying copper sulphate was the thing to use. It is green. I got the stuff today and am going to try it in my 24' above ground pool. Planning on using 4 tsp mixed with 3 gallons of water. And suggestions or precautions I need to know about before I do?.

- Soso, Mississippi USA
August 28, 2015

A. Hi A D. I just post the Q&A's, I don't even have a pool. But 4 tsp in a 24' pool shouldn't hurt anything. People seem to think about 1 part per million is appropriate (although some people don't believe in using it at all, of course). Just making sure others don't misread your comment as meaning 4 tsp for every 3 gallons -- that would be way way too much. copper sulphate is blue, so I'm not sure what's going on with your supply.


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

Q. Ted ... Thanks for your response, but I think you misunderstood me. What I meant was to mix the copper sulphate with three gallons of water and distribute that three gallons of solution around the perimeter of the pool which contains 12,000 gallons of water. I did that yesterday. I can't tell much, if any, difference yet but didn't know whether to continue to use the 3" chlorine tablets (in my skimmer), which was suggested by my pool man.

My chlorine levels have been very low even though I have used two floaters with 3" tabs in them and shocked it with two pounds of extra shock once a week; filtration system runs 24/7 all season; change filter every day ... STILL have problem with algae and cloudy water. HELP PLEASE.

A D BOUTWELL [returning]
- Soso, Mississippi
August 29, 2015

A. The use of copper sulphate to kill algae in pools can work very well if you just keep the following points in mind.
1. A safe level of copper sulphate would be 2 parts per million
2. To prevent the copper sulphate from precipitating out of solution, chelate it with citric acid [on eBay or Amazon (adv.)] before putting it into the pool.
3. Also to prevent it from making blue stains on the pool wall, correct your total alkalinity of your pool and also see that your pH of your water stays within the correct range.

copper sulphate can be bought as a powder which is very fine and it will have a greenish color, or you can get it as a blue sugar like substance, of which the latter works best. I have been using this system for years now without any problems. You also can reduce your chlorine levels to between 2 - 4 ppm where 4 ppm would be better suited for hot climates

Paul van der Walt
- Benoni Gauteng South Africa

Q. A half kilogram of copper sulphate was added to a 16,000 liter pool. What do I need to do to correct this.

Chuck Blackwell
- Curacavi, Chile
November 19, 2015

A. Hi Chuck. Some of us Americans love the metric system where the math is so easy. A liter of water weighs a kg, so 0.5/16000 = 0.00003125 or 31.25 ppm. copper sulphate is 25% copper, so your copper concentration is almost 8 ppm, about 4X what is considered safe. Unfortunately I don't see a good alternative to dumping 3/4 or all of the pool.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha - Pine Beach, New Jersey
July 2020

Q. Hi. Can I use copper sulphate in my saltwater chlorinator? My pool is about 80,000 lt.

clifford sammons
private - klerksdorp South Africa
November 25, 2015

A. Metal finishers remove the copper from their waste streams by adding sodium hydroxide to raise the pH to above 8 and precipitating out the copper hydroxide followed by filtration. You can do the same. Usually swimming pools and hot tubs have some EDTA in them, but usually not much, so you won't be able to get it all out. The higher the pH the more will precipitate out.

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


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A. I had a hard time with algae in the pool and started using a product called PoolRx ⇨
It comes in a small blue plastic container, about cup size and oval shaped, that one can drop into the skimmer basket. The chemical used is copper sulphate Pentahydrate (chelated).

PoolRx minerals dissolve out of the unit in the first 24 hours and form a stable residual throughout the entire body of water killing algae and bacteria. This frees up low levels of chlorine or salt chlorine to be more active and available. As the minerals pass back over the PoolRx unit during circulation, they are reenergized and last up to 6 months.

My pool stays algae free so long as I brush it now and then.

Al Jenkins
Retired Minister - Lakeland, Florida, USA

Q. When I was a child growing up on a farm in Africa the only place to swim without contracting a tropical disease (bilharzia) or getting taken by a croc was the farm reservoir. My father used to cast handfuls of copper sulphate into the green slimy water (way too much according to previous comments in this thread) and I'd watch the colour of the water transform itself from dark, murky, slimy green to the beautiful blue that anyone who's witnessed the process is familiar with. What I can't remember and I'm hoping someone can clear up for me (pun incidental) is whether the water became clear or remained murky (albeit blue). That detail has faded from my memory.

Thanking you in anticipation

David Brooke-Mee
- Grays, UK
May 25, 2017

Q. I have a small round plastic children's pool. We filled the pool with water and after adding chlorine the pool turned brown with iron.
What is the best way to remove iron from the pool water and what subsequent treatments should be applied.
Many Thanks

Tim Dawson
Farmer - Mazabuka Zambia
October 25, 2017

A. Hi Tim. The best way to remove the iron is with a filter. If you can get a small sump pump and recirculate the water through a bucket filled with rags or pillow stuffing it will capture all of the brown color. See topic 14995 please. Good luck.


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

A. Any filtering of a fresh iron water (pumped out from ground) will clog the filter within a short time period. To reduce or fully remove the iron (and/or other metals) a sedimentation of the water is needed prior to the use - in a tank 1 - 5 cbm. The sedimentation can be sped up by addition of strong dosage of chlorine (a handful) and a later addition of strong flocculator (e.g. alum 1/2 - 1 kg). Within 3 - 4 days the iron will settle to the bottom, clear water can be taken a few cm above the bottom.
Then only, a slow flow through a suitable filter (gravitation sand filter) will improve the water quality.
My ground water turns to dark brown within half an hour. With this procedure (tank 4 cbm in a height for gravitation flow on sand filter cascade) I get clear water for filling 60 cbm pool and house use.

Jan Mrskos
- Lampang, Thailand

A. Here in rural NSW Australia we can buy Stock Trough Blocks.bFarmers put them in water troughs for livestock to drink.They kill and inhibit algae. The are the size of very large soap bars. I put one permanently in the skimmer box basket. It degrades slowly over time

Peter Heilman
- Godfreys Creek NSW Australia

Q. I followed Garry Sunderland post based on the 50000 liter, in my case 63000 liter e.g. 350 grams of copper sulphate. 16 hours later still green. Can somebody advise? I had my pool tested 4 days before and the chemical balance of the pool was fine. Thanks

Manfred van der Brugghen
Construction professional - Johannesburg, South Africa
January 9, 2018

A. Manfred, I calculate that you would be at about 5.6 PPM copper sulphate and presuming that you are using the decahydrate version which is about 25% copper , would be a little over 1 PPM copper.

When I first cleared my pool after hurricane Irma some months ago, it took about three days at 0.4 PPM copper. So time may be on your side.

But my problem now as stated below, is a bloom of a copper resistant algae that is persisting. My online research suggests that it may be the resistant Pithophora. I need to get this solved.

John Stranahan
- Miami, Florida

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