Interesting. I've never used anything, and I have well water, so was curious why. Never had anyone recommend that to me either. I figure since they will drink out of the nastiest puddle they can find, and my well water is clean enough for us, then it's got to be clean enough for them too. I just change water every day and scrub them as needed, which tends to be almost daily in the summer since algae grows rapidly then. I rinse with vinegar to sanitize, but don't add vinegar to the water. I do give probiotics sometimes, or electrolites if needed, but that's it and those are only if needed.