All acids, including carbonic, break down any rock over time. The point of the acid test for limestones is that it releases CO2 bubbles, causing a fizz = instant indication of carbonate minerals. For best results, you should do as Rex indicated and also powder the surface if possible (use a nail or file) as some carbonates will not react even on fresh surfaces.
Keep in mind that even though a rock may not be a carbonate, it may still end up releasing Ca (and/or Mg, Na and K) and creating CO3, raising pH (slowly) over time. Especially with CO2 injection. Most igneous rocks ("granite") will be like this. This is how limestone formed in the first place. If you do regular water changes I'd presume this problem to be moot.