Ph drop after replacing dry with live rock?

[Randy Holmes-Farley Verified Community Expert]

It should have. I imagine the ph dropping was a sign of alkalinity dropping.

If it was from degradation of organic matter, that does not necessarily deplete alkalinity, just produce CO2.

Rising nitrate from organic degradation would lower both pH and alkalinity.

Lower pH from precipitating calcium carbonate obviously also lowers alkalinity.

 

[Variant]

If it was from degradation of organic matter, that does not necessarily deplete alkalinity, just produce CO2.

Rising nitrate from organic degradation would lower both pH and alkalinity.

Lower pH from precipitating calcium carbonate obviously also lowers alkalinity.

Here is what I observed with frequent testing of alkalinity using the Hanna checker along with my pF probe.

-pH dropped
-Alkalinity depletion lsightly increased, so I upped my 2 part dosing (just Part A)
-pH slowly climbed and then what was a stable 7.5 alkalinity level became 8, so I decreased my 2 part dosing
-pH continues to be high like normal and alkalinity started to drop down closer to 7.5, so now I have to increase 2 part dosing to maintain it now at 7.5

So it was likely degradation of organic matter, producing CO2, decreasing pH and the subsequent rise in nitrate increased alkalinity consumption. But now that the organic degradation has more or less stopped, we are slowly back to my "natural" expected levels.