I have never tested water for evaporation in cosmetics and have never had a problem. Then one day adding a liter to a 5 gallon tank was fatal to all fish! The water company did something and the pH of the tap water was over 9.0! Two days later back to normal, about 7.1 pH. These test strips are needed every time. You can never be sure the water company isn't cleaning the lines or whatever. Be safe for your fish, always check the water.
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