I think the main thing is you need to test to know where your tank is at (alk, calcium and magnesium) after a water
Change, and during the week before the next one.
Why is this important? Because small polyp stony coral like balance and keeping levels tight equals that balance. One of the main factors will be alkalinity to be maintained daily at the same dkh. It will fluctuate slightly at night versus day that is normal.
What you can't do is do a WC and have 9.5 alk and then towards the end it's 7.0. That will cause issues with Sps and even death or almost worse an Sps that just looks nothing like the day the guy who took care of it, sold it to you.
Calcium follows alk or the other way around. Either way you should keep that also steady. This is if you need too to keep and maintain alkalinity or calcium:
Start with say 2 or 3 ml per day of alk juice (soda ash or whatever else part you use and the calcium chloride) equal parts. You will have to test every day and log it if you want to set up a proper dosing regimen.
What you want is to keep it exactly the same for the rest of the existence of your tank. You may find your tank likes to be at 7.5 alk and the levels are all perfect like 420 calcium and 1380 magnesium and 1.026 salinity. Or it may be higher on alk.
Find your simple center and lock it up. If you do 20 gallons every two weeks don't change that ever if you can. The tank likes to be left almost alone.
I've heard this at least 6 times this year by different people, "my tank that I don't touch is the one that is the nicest" or "I went on vacation and my tank looks the best it has."
