I would bet that amount of city water you are adding, compared to the volume of the pond, as long as it's chlorine and not chloromines wouldn't be an issue. I say that because I know people that do small water changes in an ras system with chlorinated water that don't have issues.

Last edited by Cecil Baird1; 07/02/13 07:39 PM.
If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.