Whenever you add/exchange water to your pond, you should treat your water against chlor, chlorine, chloramine and heavy metals
to protect your fish and wildlive from gill burning and poisening.
If you use City-Water, and have fish, turtles this is a MUST DO!!!
If you use Well-Water, I still suggest this products, as you don't know, what kind of goddies,
your ground water includes (heavy metals such as Led, Copper and others).