Personally, I cannot stand trying to read the color charts, regardless of the brand, so much of it just seems like guesswork or approximations. Which is probably okay for a lot of tests. I used Salifert for years, but have recently decided to start switching over to Hanna as I run out of reagents for all of my Salifert tests. I currently have then Nitrate, ULR phosphorous, and Alk Hanna kits, and while they’re a little more convoluted than the Salifert tests (especially the Nitrate), getting an exact measurement is a million times better than trying to read color match tests. And the thing is, a quality test kit is around $30, so for $20 more you can get the Hanna (for which the refills of reagent are like $15, so one refill essentially pays for the difference in price). I will say though, that if I were testing more than two tanks, I probably wouldn’t go with the Hanna Nitrate test, just because it would be too time consuming, one test takes me around 15 minutes, so with three or four tanks, that could end up being 45min to an hour just to test nitrates, so that may be something to consider.