Natural way to raise PH

I have some africans setup in a 75gal tank for over a year.

I recently bought my first PH meter. I took a reading. It showed 8.0
(my tap is 7.25)


I currently have some landscape gravel in my tank. (dunno what it is)
This is not fish store gravel. I have had this in the tank for 4
years with my old oscars.

Is there something I can naturally bring the PH up?
Driftwood? Coral? something like that?
Nothing extreme..

thanks