Join Date: Mar 2017
Location: Brisbane, Australia
In short, by adding crushed coral you add calcium bicarbonate (mainly) .... this acts as a buffer (helps maintain pH) ... if your pH is low (acidic) it will dissolve more of the crushed coral until it reaches an equilibrium, if you water was less acidic, less crushed coral would dissolve, that is why even when you added a lot, it did not increase the pH more (because equilibrium was already reached) More crushed coral just means it will last a lot longer (as long as you are still adding more CO2), by constantly adding CO2, eventually the crushed coral will all dissolve, since you are constantly adding more acidic compounds
it is also worth mentioning though, that when CO2 levels are high, more will dissolve out of the water (also because of equilibrium), since water can only hold so much dissolved CO2
If you are interested in the chemistry it is described below.
When adding CO2 to you water, you decrease pH (more acidic) because CO2 dissolves to form carbonic Acid, more then the natural 3ppm (as Hobby mentioned). This acid then dissociates to form bicarbonate [HCO3- (base)], and carbonate, CO3--.(also a base), the carbonic acid donates a proton (H+) to the water (H2O) to form a Hydronium ion [H3O+ (acid)] ....
These 3 chemicals act as a buffer.
when you increase CO2 concentration, the acid can react with the bases to form clean water, and when the pH becomes more basic, it can react with the acid to also form clean water.
Even normal 100% clean water (H2O) dissociates within itself (in small quantities) to form H3O+ (strong acid) and OH- (strong base). These 2 chemicals are constantly interacting to maintain pH of 7 (neutral)
Hope you found this informative and helpful
overall crushed coral (or any buffer substance) dissolves until equilibrium is reached... it acts to maintain pH, and