I concur on the Salifert. My lfs ran out so I tried Royal Nature, one I've never heard of before and although it's like the Salifert, you use a hypodermic needle instead to add the drops to the vial and it tends to get stuck so you press a little harder and wind up adding too much and the results are not consistent, ordered the Salifert after a couple of tests with this one. Red Sea is expensive compared to the others so I've never used this kit. All these kits use the titration process.