i have a bad hard water problem down here in mexico,and when i add chlorine the water turns green.i tried everything and then my friend told me about copper sulfate.now the water is crystal clear and i hardly use any chlorine at all.it`s unbelievable and alot cheaper.i`m thinking of using it in my pool in ny this summer but don`t know if it will harm the liner.anybody know if it`s safe?