How to remove copper stains from plaster?

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I should start out by saying that I have no idea whether it's copper or not. I am theorizing because I tested a few spots with ascorbic acid and it seems to be turning black.

I have well water which is likely where my copper is coming from.

I have attached some photos of the staining. With that, I have two main questions, does this look like copper to you and it so, what is the best plan of attack?

 

[ajw22]

Use Jack's Stain ID Kit.

Then if confirmed as copper you use sulfamic acid to lift the stains and then drain the water and refill.

Copper in Pool Water - Further Reading

www.troublefreepool.com

 

[0101101001001101]

Use Jack's Stain ID Kit.

Then if confirmed as copper you sue sulfamic acid to lift the stains and then drain the water and refill.

Copper in Pool Water - Further Reading

www.troublefreepool.com

Thanks I just ordered it.