I recall reading in "Doc Johnstons" book that gill damage due to
Chlorine is cumulative. That would suggest that there is no "truely
safe" level of untreated city water to add to your pond.
Cheers. Greg

That's what the past president found out with his koi. He's a true koi-ist
and a KHA. Catches and checks his fish twice a year, etc. He was finding
gill damage with his 10% weekly water changes that he didn't add dechlor to
counteract. He also lives close to the treatment plant, so he might have
been getting a higher dose than some.

Anyway, once he started using dechlor the gills did heal over time, but
left the fish open to opportunistic crud. ~ jan

~Power to the Porg, Flow On!~