Good food for thought. I've wondered how these relatively shallow tanks affect the fish. I've also wondered about the effects of sound from all the pumps, skimmer, etc. Probably not great, but they adapt and many live much longer lives than in the wild, though some bite the dust well before their time. I have also wondered whether in the quest for stability, we may be overlooking the stength that can come from variation and occasional stresses.
I've put sand, water and snails from coastal Alabama and South Carolina in my tank, with no ill effects. I've tested the water as well. I have not used anything from coastal Mississippi - it's too close to the Mississippi River. The water is brackish, and the sand/mud is foul smelling. On second thought, I bet there is a lot of nitrifying bacteria in there though with all the nitrates from Iowa flowing out to the Gulf. Maybe there's Mississippi Miracle Mud in my backyard. Seriously though, I have to imagine that NSW and sand/mud help supply some natural things that the system needs and that may not come in sufficient supply through the live rock.
What are some easy things we can all do that will make our tanks a bit more like the ocean?