DONT GET AHEAD OF YOURSELF...LOL
Ok so from what I can gather you added crushed coral to the tank correct? has its pH value crashed?
The reason for not adding the coral is we are trying to determine what is causing your pH to crash. We need to eliminate all the possible causes.
From what I can gather here is a summary:
1) you have water sitting in glass overnight pH test out of tap and in AM
2) you have water sitting in glass overnight pH test out of tap with water treatment in....and test in AM
3) you have accomplished water change and have tested pH right after change and in AM ( USE BUBBLES like you normally would )
4) you have water sitting in glass with substrate...pH test and in AM
Ok record those values....
NEXT....if the pH stays up in any of those combos thats a good thing. If it crashes thats a good thing too because we are eliminating things.
If all the tests OUT OF TANK... your cooking ones are reading normal pH, an the tank still shows pH crash we start another set of testing.
1) Try a water change...then record pH...if it is normal for you wait another hour and test again....what is it reading? if still normal....run the test without the airstones pumping into the tank.
This will tell us if the airstones are causing the problem or contributing to it. Remember we have taken the reading with your stones running the night prior. So if the pH crashed this test will show if the airstones might be the culprit.
If the results after this test show that the pH has crashed we can probably assume that the airstones were not the problem and you can rule them out.
See...this is a process of elimination but you have to start from a known quantity and eliminate...dont go adding coral, chemicals, etc til you diagnose the problem.
Hope that helps you out....GOOD LUCK
100 Gal Planted, two Filstar XP3, Milwaukee SMS 122 pH controller, Milwaukee reg/bubble, compressed CO2, reactor 1000, 7 WCMM, 12 Ottos, 14 neons, 1 SAE, 3 German blue rams, 2 Florida Flag Fish
10 Gallon...20 Endler's live bearers planted, peat/kitty litter/sand substrate
15 Gallon...Just Schultz Aquatic Plant soil