I was using another test kit (the one with the blue Dr. fish on the package), and kept getting very high nitrate readings. I did everything - big, frequent water changes, ran carbon, searched for causes - couldn't get the reading to change. Everybody who looked at my tank said that it couldn't look that good with those kind of readings. So I bought the other kit. This one said I have basically no nitrates, which made more sense. Not very scientific, but I'm satisfied. The instructions and measuring tools lead to a fairly controlled method to follow, and while it's still comparing colors I think it's easier with the colors/card provided. If I remember correctly it even comes with an additional chemical to use a a double-check for accuracy periodically.