Chorine is what they put into swimming bath's to clear it of any impureaty's,It is a kind of very watered down anti bactierial killer,that is why you eyey goe red when you have been to the swimming baths.And anyone who says that by leaveing the water to stand a while will get rid of chorine is wrong.I had a job for a while has a life guard at my local swimming baths the chorine put in swimming water is just more consontrated it has too be topped up once a fortnight so leaveing it to stand is rubbish all you are doing is makeing it less consantrated than if you left it in a seald container.Useing a fishpump in the nutrient mix helps dissapate the chorine by been moved around the tub causeing it to evaperate ata faster rate than water.And contry to what any one says the ammounts of chorine in the water we feed our plants may do more good than bad by killing any unwanted bactiera,Has long has the water is flushed on a regualar basis it will be fine you have more to worry about what is in the feed alot of feeds have certain pripertys that when brought together produce salt. plants way of getting rid of this excess salt is through it'root system that is why it is best to flush the plants at least 3/4 times during veg and flowering.The ammount of chorine in the water that we have comeing out of our taps is very tiny.But it is a good idea to airate the water with a fish pump with a air stone on the end.