PH Up During Night

[shane]

What can cause the PH to go up during night hours in a planted tank?

I turned my PH controller on this morning and noticed it was at 7.2. The night before it was at 6.7. Prior to yesterday the pH went down at night.

The only thing that has changed is that I put a small rock in hold some more riccia (it is growing like a weed and I needed to separate it out). The LFS said it does not leach. I tested the KH today and it was about 4.5dH. I did do a water change yesterday.

I did add some excel after the water change (I never did this before). Can seachem excel cause this?

 

[shane]

Could this also be too much surface movement?

 

[Tom Barr]

Not sure what the KH was before?
Water changes, excel etc might oplay some role also.
Wait and see and I'd just worry about the pH during the day if you use CO2.

Regards,
Tom Barr

 

[shane]

The KH before was the same KH=4.5dH.