As shown here, "C-POOL MINERAL TREATMENT" is registered as a "SWIMMING POOL ALGICIDE", not as a bactericide. Clicking on their registration number link (you need to open this saved link as a PDF file) gives their label information where the product has 12.5% copper sulphate pentahydrate (3.125% copper as metallic). There is an explicit "WARNING: Staining of pool surfaces may occur due to deposits of copper salts. Excessive levels of copper will increase the probability of this occurrence."