The reef master kit is for corals, you want the saltwater master kit if youre looking for the basics.
BUT if you already have it and you are looking for phosphate, calcium, alkalinity and magnesium I would get the separate tests from salifert. More money but the results are so much better and easier to read. You don't have to get them all at once either, you can do what I did and get one test every month or so, lessens the $$ it seems. lol
You can get cheap salifert from
ReefCleaners.org | Clean Up Crews and Macro Algae - Food/Dry
The prices arent bad.....