Natural water buffer - pH adjustment??

Hi, Not sure if I'm in the right room but here goes. I'm curious to know if there is a natural way to buffer the water or add to the res to help raise the pH (instead of using pH up- down), maybe add limestone rock like they do it with certain types of fish tanks but only temporary just to raise the pH to right level. Would that be harmful to the plant or just leave behind unwanted trace elements? Anyone with experience or knowledge in this is welcome and much appreciated.