ok so since i started fish keepying i was taught that letting your water sit for 24hours will get rid of contaminates through evap.... so every week when i do a fresh water change i fill up a 5 G water bottle with really hot water nd i let it sit there intill the next water change i loose about an inch of water in there so no biggie the main question is is this practical> ? has any1 heard of this> > ?