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topic 9128, p2

Copper Sulphate as Swimming Pool Algae Remedy?

1 2

A discussion started in 2001 but continuing through 2018 . . .

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

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