Since I did not participate in the thread linked above, I'll say that I add enough dechlor for the entire tank when using a python, rather than just for the amount of water changed, because that is what the instructions say on the bottle of dechlor. Once I did forget to add dechlor and killed all but one fish in the tank by the next day, and killed all my bacterial colonies as well.
I also do 50% water changes weekly on all my tanks, even my tank that has a 6.8 ph
compared to the 7.4 pH that comes out of the tap. The pH does not swing according to my pH meter that is on this tank, FWIW