Check this out, I just ordered this and the phosphate...
https://hannachecker.com/index.php?page=shop.product_details&category_id=36&flypage=flypage-ask.tpl&product_id=227&option=com_virtuemart&Itemid=29&vmcchk=1&Itemid=29
YouTube "Hanna checker "
They have a bunch of how too's