The reason for having individual test kits is that you won't necessarily run every test every time, and that saves you money---so you only replace the element of the test you use most. A Salifert kit lasts quite a while unless you're a daily tester. Most aren't. What you need for corals is: calcium, magnesium, and alkalinity. With those three, and a salinity tester, maybe a ph meter, you're set pretty well. Buy supplements only as they prove necessary: every tank is different. I recommend Salifert, myself.