Don't know how long it will be before I have pool water to test but how often is is recommended to test or add anything to a salt water pool? I know a couple of people who have salt pools and neither of them ever do anything to theirs and it's been years since they started using salt. When I ask them, they respond by saying it looks good so it doesn't need anything. Is that true? I thought I read somewhere that you still needed to do a chlorine shock every now and then. What's the scoop?