I understand the surging water movement you're talking about. The Monterey Aquarium does a good job mimicking that. I've seen wave boxes in home aquaria do that as well. Are you suggesting I attempt that for gorgonians?
Isn't it funny, when we see the real deal, we realize how inaccurate we are with our tiny boxes!
I'm attempting to mimic a strong tidal flow, like in a protected lagoon, with the pumps I already have. I have them set up for a gyre flow pattern, which does move a lot of water, but not in a surging/rocking motion you speak of. More like a rectangular whirlpool! If I had more pumps, I'd love to mimic the tidal cycle, reversing the flow every six hours or so. I guess the ultimate flow pattern would combine tidal and surge flows.
I did take the flash light to the tank last night. Sure enough, the coral banded shrimp were out and about! I couldn't see if they were going after snails, but, like I said, they don't seem to be quite as out of control as they were before. So, between the 2 coral banded shrimp and the 4 blue legged hermits, I think I got what I wanted - a mild predation that keeps their numbers in check.