| Minh
I have never heard of "natural" stone being so uniform in size. I have not heard of this product you're speaking of.
Having a "ledge" 2-3 FEET wide is IMHO is asking for problem as water will get in between the rock and so will debris. It will accumulate, unseen, and eventually become anaerobic. That is when trouble can start with your water quality and would be the last place you'd look for the problem to exist. 12-18" for a ledge is fine as long as you have a way to "curb" the liner behind the rock to keep the water from leaking out.
You asked about whether the rock should be partially submerged - I know what you want it to look like because we have done ponds that way. It does look beautiful, almost as though the rock is "floating" on the surface. The pitfall is that when the fish are feeding, it can get pretty frenetic and they have a tendency to spook one another while eating. If a fish is near a rock edge and they get spooked they could run right into the rock and get damaged or worse, if it's a head on collision, they could knock themselves out cold. So, I would recommend the rock be place slightly above water line and not too far out over the ledge.
Mike |