Elos Calcium, Alk, & Mag
Salifert Nitrates
DD Merck phosphates
testing will depend on how stable your parems are.
I test Alk 1 x a week
calcium 1 x month
phosphates & mag maybe every month or 2.
I really could go with testing alk once a month or so, too.
if you are having issues, or changing dosing, or just a new tank, u need to test more often.