PH SWINGS

[Merv49]

My ph is constantly on the low side and swings up and down over the course of the day. At 8am it begins to rise and peaks at about 4:00pm then goes down again to lowest point at 0800.
Tank lights go on at 8:30am and off at 8:30 pm. Five light goes on at 8:30 pm and off at 7:00am.
Can anyone explain this??

 

[Randy Holmes-Farley Verified Community Expert]

It is all exactly normal.

pH rises during the day because photosynthesis consumes CO2, raising pH. At night, CO2 is produced, lowering pH again.

This has more:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

 

[Merv49]

It is all exactly normal.

pH rises during the day because photosynthesis consumes CO2, raising pH. At night, CO2 is produced, lowering pH again.

This has more:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

Looking at my Tank light schedule I can see a correlation between it and my ph swings. What I don’t get is why my fuge light doesn’t seem to show up in the equation. I have an H380 and at least 5 gallons of cheato. My fuge is lit from 8:30 pm to 0700. I would think that the fuge would help hero the ph more stable.

 

[Randy Holmes-Farley Verified Community Expert]

Looking at my Tank light schedule I can see a correlation between it and my ph swings. What I don’t get is why my fuge light doesn’t seem to show up in the equation. I have an H380 and at least 5 gallons of cheato. My fuge is lit from 8:30 pm to 0700. I would think that the fuge would help hero the ph more stable.

It likely does a little at night to bring up the bottom of the pH range, but the amount of photosynthesis (and hence CO2 consumption) is likely higher in the main tank when it's lights are on, and at night, all the main tank creatures are producing CO2, overriding the CO2 consumption effects from the refugium.