I am currently using red sea coral pro salt and the calcium in my tank is running around 500 without doing anything other than a 40 gallon water change weekly on my 220. The bucket said it should mix to around 450 to 480 but I did a water change yesterday and checked my fresh salt water mixed with our ro and it’s mixing at 520. Could my Hannah calcium tester be faulty? I don’t have anything else to compare it to and I’m wondering if this is hurting my corals ? Thanks