Copper Sulphate? Last pool cleaner seems to have used it.

[indio1919]

Just started cleaning a new pool and there seems to be evidence of excessive use of Copper Sulphate with blue and purple staining around the pump area and purpleish colour around the water edge.
Should I be worried? What can be done if anything about this staining? Im thinking the pool needs emptying anyhow as in a bit of mess with grouting etc.
Also is it poisonous?

 

[teapot]

An acid wash will get rid of it if you are emptying the pool. Not poisonous but just don't eat it! Blue veined cheese is eaten by many and the veins are made by copper, although it is believed that copper may help increase blood supply to cancers.

 

[Durk]

Not poisonous, but still nasty stuff--"moderately toxic". Consume more than a gram and you won't be happy. Don't get any in your eyes, either. From Wikipedia:

Toxicological effects

Copper sulfate is an irritant.[20] The usual routes by which humans can receive toxic exposure to copper sulfate are through eye or skin contact, as well as by inhaling powders and dusts.[21] Skin contact may result in itching or eczema.[22] Eye contact with copper sulfate can cause conjunctivitis, inflammation of the eyelid lining, ulceration, and clouding of the cornea.[23]

Upon acute oral exposure, copper sulfate turns to be only moderately toxic.[24] According to studies, the lowest dose of copper sulfate that had a toxic impact on humans is 11 mg/kg.[25] Because of its irritating effect on the gastrointestinal tract, vomiting is automatically triggered in case of the ingestion of copper sulfate. However, if copper sulfate is retained in the stomach, the symptoms can be severe. After 1–12 grams of copper sulfate are swallowed, such poisoning signs may occur as a metallic taste in the mouth, burning pain in the chest, nausea, diarrhea, vomiting, headache, discontinued urination, which leads to yellowing of the skin. In case of copper sulfate poisoning, injury to the brain, stomach, liver, kidneys may also occur.[23]

Probably very hard for stains to result in any significant oral intake. The eye issue might be a greater concern, especially if kiddie hands may be exposed to the stained areas.

Or, you could up the dose and go for this effect: http://www.artangel.org.uk/projects/2008/seizure/about_the_project/seizure