I use Salifert. I will also say that I use Tetra test strips, 20 to a little can---the dip-and-read sort used for swimming pools and koi ponds when you just need to get a quick read of a situation. I have a koi pond. I have those, and a better pond test kit; and my Salifert marine tests. Sometimes you need it quickly, to confirm something's not right, and sometimes you need an accurate, written-down, series of tests to monitor a trend. Trends are really, really, really important in this hobby. Alkalinity levels are just about as critical as is the right salinity. As you progress, you'll rarely need to look at the things you look at for your cycle: you'll not see ammonia ever when things are going well, but you will need to monitor your alkalinity, and you should do at least a monthly full series to keep your water quality up. If you start into stony corals or clams, you'll need calcium and magnesium tests as well as the alkalinity test. Brands differ in mode of reading them (color vs numbers) and go for the numerical result every time rather than color, where it's possible.