If you are not doing anything to the tank that will affect ph ie carbon dioxide , acid, lack of o2.........then as long as your tank has an acceptable alkalinity and temp then I wouldn't worry to much about ph .
Shifts are normal from low to high nightly but if it drops below 7.6 or for any reason goes higher than 8.6 then I would step in.
Keep in mind all ph buffers add alkalinity , so if you must add a buffer know that you never only add just a buffer.
Watch your corals , mainly the hard corals if ph is too off they will be the first to tell you.
__________________
........
|