I'm pretty sure that dolomite will raise pH. The general rule is if you put vinegar on the rock and it fizzes, don't use it.
I understand it will raise pH but I guess I am asking how much. I imagine it has to do with my current water chemistry but didn't know if it hits a level and then plateaus? My water is pretty hard with a higher pH, that is why I am asking. If I do large enough water changes will it not be affected as much?
As per the vinegar test, after doing much research, it turns out that although many go by the vinegar test/muriatic acid test, one can't 100% rely on this. Seiryu stone is a type of limestone that will fail the test but it is very commonly seen in aquariums. Also lace rock, texas holey rock is commonly found (which primarily you only see in hardwater setups) will also fail the test.
I am heading to a garden and landscaping place today and will probably pick up some cobblestone style rocks (really dig the smooth lines and curves) unless something really pops out at me. I really do like the look of the dolostone though.
Try this test, see if you can figure out what group of rock it is:
Mineral Hardness Testing from Rockman
Then, wherever the rock was scratched, pour the vinegar or a stronger acid in that scratch. The freshly exposed rock may bubble, where the surface that has been exposed to the air might not.
I tested it with a stronger acid (read somewhere about Nitrate Test Bottle #1) and did get some bubbling, fizzy action with that. I couldn't see much with the vinegar. So can dissolved solids be regulated through water changes where as pH not so much?
This might be a drastic example, say if you have a water sample with a pH of 7, you stick in rocks that raises it to 8. Now if you have a water sample with a pH of 8 and you stick those same rocks in, will pH stay at 8 or continue to rise?