Do you have all the other test kits you're going to need to run a reef tank?

Running as cheap as possible and reef aquariums don't really go together. If you plan on running a calcium reactor...you will need a Ca test kit as well.

You should really just bite the bullet and buy a nitrate, amonia, calcium, PH and an alkalinity test kit. In a new tank, you really need to check the parameters daily. you will be "borrowing" test kits an awful lot.