Salifert with the exception of PO4-Hanna. I will say i am at a toss up on the Hanna PO4 test between the salifert-it takes longer, has a pretty good margin of slop, and unless your using wax paper to transfer the reagent, your probably adding more slop into the test. But the number is nice.
I tried a Nyos NO3 kit and find it much easier to read than the salifert, however it takes more steps and 3 minutes longer to read and is not as sensitive as the salifert.
I use API all the time. I rarely test for anything but Ca and alk. Mg (Salifert) only like every 3rd or 4th test session (every 2 weeks). I'll test for nitrate and phosphate with API if I see anything out of the ordinary in the way of algae or cyano (very rare).
For Ca and alk I use API, but I do have Salifert test kits as a backup. I us to be concerned about the API kits because so many here do slam them as no good. The truth for me is that when I have done both the API and Salifert tests, I get results that are so close that I wouldn't care about the degree of difference. And I just find the API kits are so simple and easy to use.
API, Red Sea, and Salifert. API is not as precise, but for normal testing it gives you a good idea what the tank is doing, and if you need a little more precision like for setting up dosing or something you can break out the Salifert or Red Sea.
For a new set up?
Ammonia and nitrate for sure, nitrite if you feel the need to really follow the initial cycle of the tank.
Salinity (Specific Gravity-hydrometer or refractometer... both work if calibrated).
Most newbies check for pH as well, but it's really not a regular concern.
In time your coral will start to take more Calcium, alkalinity and maybe even more magnesium out of the water than you replace with water changes. Then you'll want to test for those and start dosing. But that's mostly for lps and sps heavy tanks becuase they are building skeletons with those.
I used to be a test junkie and tried everything out there including electronic testers. In the end, I went back to using API only for alk, ca and nitrate. I don't test for po4 because I don't have algae problem. API works just fine and I've used it for the last 5 years. Each kit lasts me over a year or until it expires. Using a more expensive test kit will not automatically make you a pro.
I'm a newbie and tank is approx 5 months old (Red Sea reefer 250). I sometimes have algae issues (cyano/brown algae) and I am using red Sea nopox to reduce relevant nutrients.
The issue I'm having is whenever I test for nitrate (API) or phosphate (Salifert) I tend to get 0 reads (other than during the initial cycle when nitrates were as high as 40ppm. I guess my question/s is:
Do I need high res test kits?
What are the best high res kits for nitrate/phosphate?
Is there an ideal time to carry out these tests (day/night)?
Should I stop dosing nopox?
I'd go ahead and use it until you have nitrate at about 5. Just wait 8 hours after dosing (say) buffer (alkalinity) or calcium or magnesium. All tanks corals or not need alkalinity testing. A good reading is 8.3.