Does water cure assist anything other than chlorine break down.

i actually do use old fish tank water for all my cannabis. It imparts a full microbe inoculation for your soil, if your fish tank has live plants in it. And to answer your question, no letting water sit out only works for chlorine it will not get rid of chloramines which are widely used in addition to chlorine. Chloramines have to be removed by chemical or physical process. I use Seachems prime to treat my water before it goes in the fish tank. You can find prime in most Aquarium retailers.