kj5kb is right in that gravel suitable for concrete would be about the same in physical character anywhere. The trouble is that some places they will break up limestone to make it the right size which would make a very sharp, pH raising mess in an aquarium while in other places they can just dig up gravel and sort it by size. The chemical nature of the gravel will vary a great deal. The sharpness of the gravel will also vary quite a bit based on how its obtained. Sand for making concrete is often specified to be "sharp" so that the concrete will bind together better so it is not what you would want if you are worried about the sharpness of the particles.
