I agree that Salifert kits are good, and I have gone through dozens of them, but recently tried some Red Sea and API kits and they are generally easier to use but also don't generally have as precise measurement (like the Red Sea Nitrate kit minimum measurement is 2ppm where the Salifert measures to 0.1ppm). I would always use Salifert but wanted to try a MUCH cheaper alternative. Once my system is running good and stable I won't test much anyway.