LaMotte's alkalinity is a good one but more expensive. API and Elos also good for alkalinity. API and Elos for Ca. Merck or Hanna Photometer for phosphate, anything else is wasting your money. Salifert or Red Sea (measures off a bit, but not critical on Mg) for Mg. Elos, LaMottes for nitrate. Salifert for strontium, but very hard to use. These are ones I've used and found acceptable. I can't recommend Saliferts anymore for the common tests because they've had some QA issues as of late.