best test kits for Ca and Mg?

[Ron99]

As the title says what do people recommend as the most accurate test kits for Ca and Mg?

I have an Elos Mg kit that is giving me a reading of somewhere around 1050 for Mg in a freshly mixed batch of D&D H20cean salt at a SG of 1.025 and temp of about 78. That seems a bit low as I thought this salt should be higher.