That's why I said copper pennies.
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Thanks to all who replied. Will not use the bluing. Will continue to use apple cider vinegar since it helps to cut down the speed in which algae grows. Waterers are shaded at all times to keep the water cooler. My ducks drink from the same nipple waterer as the chickens so need to be careful about the amount of copper in the water so copper pennies won't be used either.