I use many different kits for a variety of reasons. I like Red Sea for Mag, Hanna for Alk and Salifert for Calcium. That has happened through trial and error and finding that I like and trust different ones for different things. I also use the Hanna checker for Phosphate because I really could not read the end point color on others that I tried. That being said, I wish Hanna would develop a liquid version regeant for the Phos test, getting the powder into the vile is ridiculous and easy to mess up.