A lot depends on where you live as different areas have different amounts of chlorine. We are lucky where I live as there is no chlorine in the water so I do not add anything to the water and don't worry too much about the temperature either. Some fish are more sensitive to such things than others.
Fishless cycling is big overseas at the moment and seems to be the latest fad. It is hoped to save the poor fish when people go to their lfs and go home with a tank and chemicals in one hand and a bag of fish in the other and told to just add the water, plug in the heaterstat and add the fish :roll:
Using fish to cycle a tank is perfectly acceptable, when done properly, but too many people are impatient to add more fish too quickly and then wonder why their fish die, they get white spot outbreaks, and their water goes green.