Rising and dropping PH

[JParra]

has anyone experienced the following, If so what was the cure?

when the lights are off, my PH is at 8.2, then it rises up to 8.4 up until the lights go off, and drops back down to 8.2. is it safe for the PH to go that high?

[pyrrhus]

totally normal dont worry about it.

[EtOH_is_good]

normal variation. photosynthesis has stopped, so they become net oxygen users instead of producers. this is why some refugiums are on "reverse" light cycyle with the main tank, so that the CO2 levels don't flutuate due to photosynthesis.

[ReefinReefer]

Your pH swing is better than mine.

If I forget to do an overnight kalk drip, then my pH swing goes from 7.8 wee hours of morning (before lights on) and at the end of the day (just before I turn lights off) it goes to 8.2

 

If i don't forget the kalk drip its alot better at 8.0-8.2 swing

[shadofax69]

Just a quick correction. The plants don't become oxygen consumers they just stop uptaking CO2. When they stop uptaking CO2 it reacts with water to form carbonic acid which lowers the pH. When photosynthesis starts again CO2 consumption picks up and the concentration of carbonic acid decreases and the pH raises. And yes this is normal but may cause stress for some tank inhabitants.