"Nedra" wrote:

But would it not depend upon how Much water is being
topped off?? I think I would add some DeChlor every
other day or so- just to be sure the Chlorine wasn't poisoning
the pond.

Yes.

With auto-topoff the amount should be small, under 10% per day.

Adding some declor, just in case, is good. So is using activated carbon
in your filter system, either before, or after the water hits the pond.