I can tell you the use of copper power and the Hanna checker have made this so much easier for me. I raise the tank .25ppm per day until reaching my target of 1.75ppm. All of the current Wrasse are eating as if copper is non-existent.
I ave asked Hanna in the past and they told me that their Copper checker would not work in saltwater. Maybe worth checking with another test kit or contact Hanna to be sure you are getting correct readings.