Fluctuating pH in planted tank

[Sprae]

Hi guys, I've noticed that my tank pH is 5.8 during the day but goes higher to 6.0. Is that normal?

As many of you know, I have loads of moss and an anubias on a driftwood.

[fishmosy]

Completely normal. Its all to do with CO2 (carbon dioxide). CO2 reduces pH because it forms a weak acid when dissolved in water. During the day, your plants use up CO2 for photosynthesis, thereby increasing the pH by removing some of that weak acid created by the dissolved CO2. Overnight the plants release CO2 instead, causing a reduction in pH.

Also remember that since shrimp tanks are often low in minerals, and also in your case already acidic (pH 5.8 to 6.0), it doesn't take much change in CO2 (or any acid for that matter) to cause a large change in pH because there are few mineral ions to buffer against the acid.

[Sprae]

Thanks fishmosy. I have lights on from 2pm-10pm (8hrs) so photosynthesis in that period should raise my pH?

[fishmosy]

Absolutely, i wouldn't be surprised if you noticed a difference in pH in as little as 1 hour after your lights come on, depending on the accuracy/sensitivity of your pH test of course (e.g. Digital pH meter vs. pH colour indicator)