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topic 9128 p2

Copper Sulphate as Swimming Pool Algae Remedy?

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A discussion started in 2001 but continuing through 2019

July 17, 2015

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 24, 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

August 22, 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 24, 2015

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
Aqua Pools - Central Florida, USA

August 25, 2015

Q. Thinking of trying copper sulfate 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 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
Pine Beach, New Jersey
Striving to live "Aloha"

August 25, 2015

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

Christie Miller
- Houma, Louisiana

August 25, 2015

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

Melanie Quim
- Anderson, Indiana USA

August 28, 2015

Q. I saw a post of Facebook saying Copper Sulfate 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 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
Pine Beach, New Jersey
Striving to live "Aloha"

August 29, 2015

Q. Ted ... Thanks for your response, but I think you misunderstood me. What I meant was to mix the copper sulfate 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.

- Soso, Mississippi

August 31, 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 sulfate would be 2 parts per million
2. To prevent the copper sulfate from precipitating out of solution, chelate it with citric acid 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

November 19, 2015

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 25, 2015

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 27, 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
Plating Systems & Technologies, Inc.  
Jackson, Michigan, USA

February 1, 2016


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

May 25, 2017

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

October 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 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
Pine Beach, New Jersey
Striving to live "Aloha"

November 5, 2017

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

November 6, 2017

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

January 9, 2018

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 14, 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

January 14, 2018

Q. After a few months of clear water with copper treatment, I am now having a bloom of a copper resistant green filamentous algae. My copper concentration is 0.4 ppm as determined by the LaMotte 3619 Copper Test Kit. pH is maintained under 7.4.

It's been going on for a few days now with no sign of abatement.

I do have a residual, from the previous Chlorine system, of 150 ppm Cyanuric Acid, i.e. stabilizer. Also when I a add more copper sulphate, I don't see a rise in concentration beyond the 0.4 reading which has me puzzled. Could it be the residual CYA?

I read about a copper resistant green filamentous algae so I guess I have it.

What should I do?

John Stranahan [returning]
- Miami, Florida USA

January 17, 2018

A. Sounds like you've got a nasty algae there.

First off, I'd reduce pH to 7.2 or 7.1 This will make the copper more soluble and more effective.

Then I'd hit it HARD with chlorine, calcium hypochlorite, until you get up to 4 or 5 ppm which stays up overnight. If you pool is heavily infected, you will likely have to make multiple adds over a few days. If yours is a typical 16' X 32' pool, you might end up using 5-10 pounds or more of hypochlorite. As you kill it off, keep back washing your filter to get rid of the dead stuff.

Consider NOT using CNA. In my opinion it causes more problems than it solves.

You CAN kill it.

jeffrey holmes
Jeffrey Holmes, CEF
      South Carolina

January 17, 2018

Rereading your post - "the previous Chlorine system".

By this do you mean that you entirely stopped the use of chlorine and relied only on copper?

If so, that's wrong. Copper is highly effective against MOST forms of algae, but not all. And copper is ineffective against other possible nasties - bacteria, viruses, odors and others.

Chlorine is absolutely a necessary component. It should be abt 1 ppm at all times, with an occasional boost to 2 or 3 ppm.

jeffrey holmes
Jeffrey Holmes, CEF
      South Carolina

January 20, 2018

thumbs up sign Solved for the time being.

Thank you Jeffrey for your interest and comments.

This situation came about from the pool owner (I've offered to help her with the pool care) having used trichlor tabs exclusively for chlorine titer. Like with so many that I have read about online, the cyanuric acid (stabilizer) in the tabs builds to problematic concentrations. It remains as the chlorine diminishes. She is adamant about not draining half or more of the pool to reduce the CYA concentration. At the present concentration of 150 ppm, chlorine action is reduced dramatically, requiring very high chlorine concentration for control.

Since the pool is solely ornamental during the winter and since it is only she who uses the pool occasionally in the summer, pathogens are of no concern now and human contagion never.

So I thought that I would give "copper only" a try by using copper sulphate as available economically as root killer at Home Depot and Lowes. At 0.3 to 0.5 ppm copper it cleared the pool of algae after Hurricane Irma and did well until I got a copper resistant strain a few weeks ago. It is consistent the online description of the copper resistant Pithophora, a green filamentous algae.

Knowing that copper is allowed in drinking water up to 1 ppm I decided to see if I could get some algaecide action at 1 ppm since it is still safe for humans at that level.

After three days at 1 ppm copper the pool is now clear. The plan is to now maintain the copper concentration at or a little under 1 ppm.

When the season rolls around for her occasionally using the pool I will sanitize it to 1 ppm chlorine for pathogens.

So for now all seems to be in order. I've read the warnings about the black stains resulting from chlorine copper interaction but that is to be seen or not.

BTW, the patches of black algae on the pool wall have disappeared since using copper sulphate, without any scrubbing.

John Stranahan [returning]
- Miami, Florida USA

January 19, 2018

Q. I have now used Aqua Pro 'Algaecide' 2 liters in my 63000 liter pool, it is clearing up and getting blue again. My question, however, based on the previous posts, is whether one can maintain the Algae with the 'Copper sulphate' powder one can buy at the Chemist. Can anyone advice how much to use and timetable?

Manfred van der Brugghen [returning]
Construction Professional - South Africa, Johannesburg

January 20, 2018

A. Maybe you can use plain copper sulfate, but it's solubility is limited. IF you keep your pH on the low side, say 7.1, it may be soluble enough.

Much better to buy chelated copper sulfate based algaecide which is freely soluble. It doesn't need to be expensive since it is essentially permanent, being lost only when you remove water.

jeffrey holmes
Jeffrey Holmes, CEF
      South Carolina

January 20, 2018

thumbs up sign Thanks Jeffery, will give it a try.

Manfred van der Brugghen [returning]
Construction Professional - Johannesburg, South Africa

January 31, 2018

A. In fact, Copper Sulphate is very easily soluble. Prior to dispersing into the pool water it is good to add half of a cooking ladle of CS (ca. 150 gr) into a bucket with water (ca. 10 l), and mix it. Then, taking out continuously the dispersed solution from top and distribute it into pool while filling up more water into bucket and mixing, taking out again, etc., until all the blue powder is dissolved.

Jan Mrskos
- Lampang, Thailand

May 17, 2018

Q. After deliberately increasing the copper concentration to 1.4 ppm to kill off a resistant strain of algae I now need to reduce that concentration to below 0.5 parts per million to get the pool ready for swimming season.

What I am looking for is a low-cost method of decreasing the copper concentration. Methods available via pool supply stores cost over $100. I'm hoping to find something lower in cost and PROVEN to work in swimming pools with common pool filtration systems. Any information on this would be greatly appreciated.

Jon Stranahan [returning]
- Miami, Florida

June 23, 2018

A. We have an 18' round 54" deep above-ground pool. Every summer we only buy three things …

We already have a small box of copper sulfate we bought at our local tractor stuff store. We mix 1-1/2 cups of the bright blue granules in a 5 gallon bucket of clean water. Stir until all grains are dissolved. We walk the perimeter of the pool in the afternoon and pour all of the mixture in. Then (here's what we buy) we walk around again pouring 5 gallons of HOUSEHOLD bleach. The cheap stuff works for us but don't use laundry bleach. It has less chlorine in it. After adding 2 chlorine tabs (3") to the floaty thing. We wait usually 2 days with the pump on full time. Backwash and rinse our sand filter 2x per day.

By then the water is blue but still can't see the bottom. A trip to the "garden and pool" center at the local WALL place for a bottle of clarifier. This coagulates (clumps together) the now dead algae and brings it to the surface so the filter can more easily filter it out. We walk around the pool pouring straight from the container about half of the thick blue liquid. Again keep the pump constantly running. A day or two later we can usually see the bottom and all the muck. Once we vacuum, this stirs up more stuff (we vacuum while in pool) after that we use the rest of the clarifier in the same manner as before.

Don't get in the pool if the water is green. This could be live algae and getting it in ears, nose or mouth could cause problems. Don't use any more copper sulfate. You can test it if you want but we find our measurement works for us. We only use one dose of copper sulfate upon opening the pool. Only once did we use it twice because we had a very very rainy summer, weren't in the pool often and let the chlorine tabs run out. We haven't had any blond haired beauties turn green on us. We don't use shock either. If you use too much clarifier it could make pool a "white" cloudy. But it will filter in a few days. We are usually vacuuming at 4 days and are swimming about 7 days after starting the routine. We use the recommended dose on the box of copper sulfate for the gallons we have. Use the internet to figure your gallons if you don't know. Have been using this in our above ground with the original liner for 15 years. We do have a sand filter but no ionizer or UV filter or heater. So I don't know if you should use with these. Hope this helps.

Judith Brewer
- Hohenwald, Tennessee, USA

July 2, 2018

Q. My situation: Hi, we used copper sulfate in our 27' round, 4 1/2'deep pool. My question is, what can I use to raise the hardness, total chlorine and free chlorine? They are all showing 0 on my test strip and I don't think I can use shock.

Jan George
- Tyrone, Pennsylvania

July 8, 2018

A. No worry about Copper Sulphate, the pentahydrate (CuSO4·5H2O), the most commonly encountered salt. Copper (Cu) is allowed e.g. in German standard for drinking water up to 2 ppm. And Cu is contained in CS just by 20 - 25%, i.e., with 8 - 10 ppm CS you get 2 ppm Cu.

During next days the Cu is depleted by reactions with algaes and other unwanted substances in pool water, hence it will be filtered out, backwashed and vacuumed from pool bottom.

And/or farther dissolved by rainwater, by additional water after backwashing, vacuuming.

After CS dissolving it is better to stop the pump and let the CS work. When later added a flocculant (e.g. Alum - a wonderful substance formerly used by our fathers for stopping bleeding after shaving), all will sink to bottom.

BTW, the algaes are not harmful, they just keep the water from being crystal clear, beautiful for our eyes.

Jan Mrskos
- Lampang, Thailand

November 16, 2018

Q. Hi. I need to know how much Copper Sulphate to add to drinking water to remove Algae and I believe any protozoans or coliform bacteria which I also believe are sensitive to CuSO4?
My storage tank is 5000 Litres.
i.e., how many grams to 5000 Litres.

Many thanks.

Jean-Pierre FOURIE
- Harare, Zimbabwe

November 2018

A. Hi Jean-Pierre. Garry S claimed that 1 ppm ^ copper is quite safe, and estimated that ^ at 0.5 ppm 100-120 grams ^ copper sulphate would be required for a 50,000 litre pool (meaning 10-12 grams ^ copper sulphate for 5000 litres). Jan M says 2 ppm ^ copper is safe per German drinking water standards. The USA EPA limit is 1 ppm ^ copper. WHO seems to accept 2 ppm but lean towards 1.

This should cover it if you're talking about your own family's drinking water. If you have responsibility for someone else's I think you need to work on a deeper level with regulatory agencies.


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

November 17, 2018

Ted Mooney, P.E. RET

thumbs up sign Thank you so much for that information. That's exactly what I required. The promptness of the answer was impressive. Thank you again.

Jean-Pierre FOURIE [returning]
- Harare Zimbabwe

November 19, 2018

The 1 or 2 ppm is a limit of Cu for drinking water. Since CopperSulphate contains only 20 - 25% of Cu, the limit for CS can be 4 - 5 ppm (when Cu 1 ppm), event. 8 - 10 ppm (when Cu 2 ppm).

Jan Mrskos
- Lampang, Thailand

November 2018

thumbs up sign  Thanks, cousin Jan. Garry S suggested 0.5 ppm of copper for algae control and said that it equated to 100-120 g for a 50,000 liter pool and his calculation was correct and based on your copper percentage of 20-25%. For Jean-Pierre's 5,000 liter water tank, that would scale down to 10-12 g, so hopefully we gave him the answer he sought.

But you are correct that my posting was confusing in 2 ways --
-- not making clear which numbers referred to copper and which to copper sulphate (which I have now repaired with superscripts, and
-- reverting to Garry's 0.5 ppm of copper for the calculation while saying 1-2 is probably okay. Thanks for the catch.


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

February 14, 2019

Q. I have just started to use copper sulphate to try to keep my tile joints clean after spending 4 days cleaning them by wire brush and gaining aches and pains in the process. I note that people are talking in terms of PPM, but how is this measured? Is it simply the number of grams of CS granules divided by the total number of grams of pool water x 1 million?

David Ballinger
Retired civil engineer - Pattaya, Thailand

February 2019

A. Hi David. You are right about PPM meaning parts per million, but uncertainty is introduced when you ask a 3rd party what someone else meant :-)

Some people might mean parts per million of copper (Cu), others might mean parts per million of copper sulphate (CuSO4), and some might mean parts per million copper sulphate pentahydrate (CuSO4·5H2O = weight of the crystals).

Copper sulphate pentahydrate is 25.5% copper by weight, so if you want 1 PPM of copper you need to add 4 PPM of crystals. Good luck.


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

February 15, 2019

thumbs up sign  Thanks to Ted for his very quick response to my query. An on-line pool supplier in Thailand recommends that CS should be added at 3 gm per cu.m. of pool water. A cu.m. of water weighs 1 million grams so based on the above recommendation the proportion of CS in solution will be 3 parts per million, producing slightly less than 1 ppm of copper. The recommendation goes on to say that this treatment should only be done twice per year to avoid build up of copper with its undesirable side-effects.

David Ballinger [returning]
- Pattaya, Thailand

February 22, 2019

A. Once you are frequently backwashing the filter and vacuuming the bottom (I do it mostly in one go) you have to add fresh water. Consequently, the concentration of the Cu is slowly reduced. And that beside the fact, that the Cu is also diminished by reacting with the algaes. Therefore a timely addition of a new CS portion is needed, especially in the springtime.

As a matter of fact, when e.g. the German standards for drinking water allow 2 ppm of Cu, the 2 ppm in the water for swimming should not make any harm, even if it is a bit over. The 2 ppm does not mean that a tiff or two of it is poisonous, the value is for a precaution if it would be permanently drunk over a longer period of time.

With treating the swimming water by CS we spare ourselves of the daily hassle with keeping a high level of chlorine (to kill the algaes) and also of the difficult (and expensive) job of maintaining of the pH, that is for the chlorine effectivity important but not for the CS.

Jan Mrskos
- Lampang, Thailand

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