I read something about this topic and I don't know if it's Alzheimer but I don't remember much of it so I can't give you any clear and concise answers.
There are somewhere (again Alzheimer strikes) here in the FAQs a link to a site with "reef chemistry" or the like, maybe advancedreefers or so, that explains it well but as nobody has answered so far, I can give you at least a few sketchy hints.
Some authors suggested that a ph even around 8.6 wouldn't be that bad at all.
Alkalinity is like a reserve. It's a buffering capability maintaining a stable ph. In natural seawater, the alkalinity is quite low. There is not much buffering needed due to the sheer volume of the ocean.
It exists also some disagreement about the range of alkalinity. It depends on the specific tank how much alkalinity is needed as the ph gets lowered mainly by CO2 from the air and by acids from rotting food and waste products from the critters in the tank. But 12 dkH is often regarded as the upper limit to aim for.
Calcium is often added by kalkwasser. This solution raises your ph and your alkalinity.
If you add an alkalinity agent it will raise your ph, too. As I stated above, I'm not sure why but IMHO it's the carbonates and bicarbonates that first raise the ph and then stay present what raises the alkalinity. When those carbonates get consumed from CO2 and other acids you need to dose kalkwasser again.
But as the carbonates act as a buffer, you can raise easier the ph than the alkalinity. In fact, there is also the concentration of calcium, magnesium, boron, and maybe strontium in that order that form a trangle of dependencies with alkalinity and the ph.
There is also a subtile difference between the definitions of alkalinity - a more practical and a theoretical one. That makes understanding somewhat more difficult, too.
Take my hints only as a first step because I would have a bad feeling when I would need to appear at some chemistry test.
to these methods.
