No, haven't ever tested for strontium in all the years (40) of keeping
SW aquariums. Doing regular water changes should keep your strontium at proper levels. Just because a manufacturer has a product on the market doesn't mean you have to dose it. Strontium is found in minute amounts in
NSW and is not required to dose if you are doing water changes. It's possible your Strontium level is so high the test kit goes berserk.
I would stop dosing and let it settle for a few weeks and test again. I, personally, would not dose it.
Dick
