PH and Nitrate.
Just had a good conversation about "ranges" and "consistency" being more important than "spot on numbers"
i.e. every time you test your water, if you're testing it the same exact way everytime, and your tank is happy and healthy and growing, you've set up a "range" for yourself that's working. If you do your test the exact same way every time you should become super familiar with that range and coloring of your testing. Therefore making it easy to spot when something changes.
i.e. if you use API, and only use API and use it all the time, and are getting consistent readings. That should be good and efficient. forget if it's 0 or >.25 to you. who cares if things are healthy and happy.
If you're then micro dosing or specifically dosing you'll be able to easily spot the changes, or should be able to notice the change easily, but it might be hard to get exact numbers.
like, basically buy an API test kit and test every few days until you do 50 tests or so and you'll now have a complete feel of your tanks parameters.
Then by using more advanced checkers i.e. Hanna you can basically just use them for more precise and accurate minimal readings such as for Phosphate and or Nitrates if you're trying to take them from 0 to a nominal amount for increased coral growth etc.
With an established tank this would be completely usable,.
I think the only difference is for new and beginning reefers, getting used to the testing is a learning curve.
Maybe you could get a 1G water sample from your stores best Display tank and practice testing there, to get idea of good parameters from an established healthy tank and a general feel for testing.
Doing this and being able to buy the cheaper tests might be a good option for people looking to save money instead of getting these $50 per element testers.
