Storing nutrient solution

Lid closed in a cool dark area is ideal, no longer then 4 days like leftovers. airtight if possible. If there is room in the fridge its good. Or freeze it and let it thaw out on the soil line in summer like how some people water orchids. Air stone can help like @Organoman suggested, it will also promote aerobic bacteria vs anaerobic and that can sometimes be a bonus. To @UBU's point, chloramine does not off gas, but you can destabilize it with UV or Vit C aka ascorbic acid then it can be off gassed. But there is so little in the water its not going to affect the grow greatly. Cannabis does not seem to be overly sensitive to CL from my experience with it, unlike some carnivorous plants, they can be really picky. Good Luck!