Ph drop why?

pH normally fluctuates between day and night. It will be lowest first thing in the morning when you turn the lights on, and highest at the end of the day when you turn the lights out. This has to do with algae photosynthesizing and removing carbon dioxide from the water. In the absence of light, photosynthesis slows down and carbon dioxide builds up. It bonds with water to create carbonic acid, which drops the pH. This is why when the tank is dark, pH drops. When the light comes on again, more photosynthesis starts up, the carbon dioxide is used up, and the pH rises.
 
This is also why a lot of us that run refugiums in our sumps run the sump light reverse light cycle to the tank. So when the tank light is off the sump light is on. Just a way to try and stabilize the ph.
 
I know my pH goes down to almost 7.8 when I turn off the lights and if I do a test in the morning but floats around 8.0 during the day. I am not running a sump on this tank but the fish and the zoas that I have seem to be doing fine.
 
For the most part its not something you have to really worry about unless you are doing a lot of sps..which I am not but since I have a fuge running I do the reverse cycle anyway...I figure if I can keep something more stable then why not.
 
For the most part its not something you have to really worry about unless you are doing a lot of sps..which I am not but since I have a fuge running I do the reverse cycle anyway...I figure if I can keep something more stable then why not.

+1 here
 
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