Why is my PH rising?

[Gripenfelter]

Still goes up. Not as much but still going up.

When I re-calibrated the probe it went to 8.13. Down from 8.37. All yesterday it was at 8.19. This morning when the lights came on it was 8.22.

I have my RO/DI unit set to run for 30 mins per day to top off the water.

Nitrates and Ammonia are 0.

PH test verified probe reading.

Sump gets lots of bubbles from overflow.

[Myka]

How old is the probe and what brand? Often times when probes start dying they start losing their calibration.

Fwiw, CO2 isn't the only cause on low pH. Decaying organic matter will lower the pH as well which is why many tanks that have high nitrate also have low pH.

Originally Posted by The Grizz

According to my Ph probe my tank is sitting @ 9.09.

I doubt that is accurate. Have you calibrated lately?

[Gripenfelter]

I verified the probe reading with an actual PH test and it's accurate. Seems to be stable though. Still sitting at 8.19 over night and 8.22 during the day so not bad.