Alkalinity is one of the basic water parameters you should be testing. pH is kinda irreverent, as it does swing throughout the day and night. Alkalinity is also what determines how much or how far the daily pH swings are. Higher Alk
means less pH swing. Unfortunately corals absorb that which makes up alk
(i.e. carbonates), meaning the pH swings can increase as time goes on.
Having an appropriate pH level (8-12 dKH
or about 3-5 meq/l) will bring your pH level up to the range you want (8.2-8.4), so manage the alk
and let pH follow on its own.