I'm going to have to disagree with the first point. Lots of pressure available means that the agitation is more vigorous when they are deeper. I have tested and verified this. More water is moved the deeper the stones get, and the surface agitation is visibly greater.
The second point is a good one, though, and was why I had placed them in a corner of the pond. I'll see if I can rig a way to get them farther up the steep side, once the ice thaws enough again for me to move them.
