You want to lose the coral becase a) it is not needed unless you have extremely soft water, and b) because it screws up the C02/kh/ph relationship.
so that there is no way to tell how much CO2 you actually have.
Now, if you have very soft water you may need to buffer it up a bit. Some need to, but it is rare.
I like to keep things a simple as possoible, the less I add to the water, the happier I am.
Keep in mind, adding CO2 to water forms carbonic acid. The more CO2, the lower the ph. Lower ph means the quicker the coral gets disolved. Having petrified wood in my tank screwed things up so much, I lost a few fish before I figured it out.
90 Gallon, eco, pressurized, controlled, 240 watts.