Ascorbic Acid (VitaminC) One of the most efficient, cost-effective, and fastest ways to neutralize both chlorine and chloramine in water. 1g does over 30 Gallons almost instantly.
Not only that
Ascorbic acid is a powerful antioxidant (a reducing agent). When you add it to your nutrient solution, it lowers the Oxidation-Reduction Potential, (nutrients become much easier to uptake) butt shhh thats our secret. There is no better option than a 3 dollar bag of ascorbic which last forever. Anything else is snake oil.
Not recommended to let water sit to evaporate the chlorine, the chlorine will evaporate but if there is chlorine then there is also 99% chance chloramine is present which does not evaporate, if left in presence of any organic material it will form clorophorm and other toxic THMs. Its not going to seriously harm you in small quantities but jone the less id prefer 0% chloramines. Best option is and always will be ascorbic acid.
Only caveat is you can't really use it in DWC setups as it creates a biofilm after a couple days clogs shit out of lines.
So I guess its a good bet if your doing dwc otherwise check active ingredients.