I think reefvet is trying to get you to understand the single most important thing about keeping sps corals alive, to thrive the concept gets deeper. You would likely see many more tanks if sps keeping were easy, it is in fact quite complex. I will however try and simplify as best as I can for you, however, I would strongly encourage you to go to the sticky's on this page, and read, read, read, assuming you want the challenge?
#1 Big Three (Calcium, Alkalinity, Magnesium)
You will need to understand that sps corals, clams, snail shells, coralline algae, are all examples of invertebrates that consume alkalinity, calcium, and magnesium. These parameters need to remain stable in order for sps in particular to survive. So in order for your corals to grow, they consume these minerals, so you need to add the minerals back into the tank, as they grow, the consumption changes, for this reason, you need to purchase quality test kits. I personally use Lamotte for Alk, Salifert for Calcium and Mag. When you begin to add these corals to the tank, then begin testing, you will see how much per day these corals take in. For example, if I had a total of 100 gallons, had only a few sps corals, I would start with a test of my current water, then add 10ml of each, then the next day, at the same time, I would test again. See what your test reveals, if it is the same as previous day, your tank is currently consuming 10ml per day, and until the corals grow, or you add more corals, likely you can keep that dosing schedule for awhile. When I establish my base line for Ca, and Alk, I usually test everyday at the same time for over a week to dial in my consumption. Magnesium in my opinion is not something I am too concerned with, I test weekly, but see little consumption, so I only dose every so often, however, you need to stay in proper range, if not you will precipitate your calcium and alk rendering it useless, so mag does need to be in range for the ca, and alk to work. I prefer to keep my parameters at close to Natural Sea Water range, or NSW.
I test at 7.33dkh for alk, 400ppm Ca, and 1390 for Mag. Just my preference, my salt tests roughly at those levels, so when water changes are made, I stay in those ranges and do not have to adjust my dosing schedule, because if I for example did a 20 gallon water change on my 120, and it ran at 11dkh for alk, and 420 for Ca, I would raise my total volume to a higher level than normal, which certainly impacts my levels of parameters, and changes my dosing schedule for a few days. For this reason, I find it very important to use a salt that is in the range you wish to keep your parameters set. I use Neo salt from Brightwells, it tests very close to what I prefer my levels at, so I do not have to worry when changing out water, my dosing is automated, so having to change my schedule every time I change water would be a hassle. Keep in mind, I use 2 part dosing, however, you can use other methods to keep parameters stable. May I suggest the use of kalkwasser until you understand the importance of keeping calcium and alk stable, since it keeps both stable in a one drip solution. Essentially it is pickling lime, added to fresh RO water mixed at up to 2 tspoons per gallon, and dripping at the rate that your tank needs to make up for evaporation. So when you start, maybe your solution is at .5 or .75 tspoon per gallon, as your reef grows and the demand for consumption grows with calcium and alk, you then use more of the pickling lime per gallon, up to 2 tspoons, after that you have to make another choice for keeping your parameters up. You can also research Calcium reactors or balling method, both of which I would not think about until you become more experienced. OK, I am winded, I think that should give you some where to begin, hoped this helped you, I do think you need to read, read, read... Good luck.
Again, choose your salt based on YOUR desired parameters, Red Coral Sea Pro is elevated in Alk, reason I never used it. As far as food goes, have a health stock of fish, well fed, with a powerful skimmer is all you need for coral health, that and strong light, now go have some fun 
