Why is my PH rising?

[Bblinks]

Originally Posted by Gripenfelter

PH has gone from 8.08 to 8.37 in 4 days. Using a PH probe.

Don't use CO2 or any reactor. Just refugium and 2 skimmers.

What causes PH in a reef tank to rise?

Corals and fish seem happy but I'm concerned over the rise.

you don't dose anything I assume, so first I would recalibrate your ph probe to make sure its still within proper working range. It would be beneficial if you can get another tester to confirm your findings. reason I said this is ph usually drops by itself not rise.