Goldfish do fine in hard, high pH water.
What is your pH, gH, and kH? Most likely anything you add to neutralize the water, if you have hard water, is only causing a temporary drop in pH, and it will rise back up to the normal pH pretty quick.
A neutralizer shouldn't be necessarily unless you have extremely hard water with a VERY high pH, which isn't likely. Your fish are better off with stable water perimeters than trying to change the pH to fit what you assume the fish need.