No. You wait for the chlorine, heavy metals, chloramines, etc. To deplete, and vanish, or dilute to safe levels. adding a proper dechlorinator, such as Aqua Safe, and Seachem Prime. Will almost virtually instantly take out the above listed harmful substances. In a 2.5 gallon, you should do 1 100% water change, and 1 50% water change weekly, with one make betta