ive heard good things about salfert and red sea, i use hanna checkers for po4 and alk, but i just ordered red sea (alk, cal, mag) and am going to compare notes.
+1 on the red sea. Seems to work good. Haven't tested for nitrates or phosphates in forever. Is it just me or does the colour change on the Alk seem to be a little more subtle than the cal and mag.
Love how easy and quick the hannah alk one is. Use this one the most, then hannah phosphate...bit tedious adding all the powder into vial though, but easy enough. Calcium, Mag, and Nirtrate I use and recommend salfert.
What I like about the red sea is you can get the refill kits. So when your kid does what mine did and spill a brand new bottle of alk solution, it only costs 11 bucks.