My parameter are all fine, but i have extremely hard water and you can smell the chlorine in the tap water. So my thought were if I was to do two changes instead of one the afffect that the chlorine would have on the tank would be demnished. Now I use prime clear up the chlorine every time, but as i said smaller volume should have a small affect on the tank.
If you are using Prime, chlorine won't be an issue regardless of how much water you change.