One other thing I have noticed in the past is that the guests in the grandstands don't always see the show tank! I had a couple situations where the people were getting angrier while watching the show - they were not hungry or tired (much). It's usually when the top rail of the tank is right at ground level. I now always put the show tank up one level above the path in front of the grandstands, and folks are happy. You can put it higher up, but it just doesn't look realistic.
Someone mentioned that the top of an exhibit tank that's level with the ground also can't be seen into, but my last contest zoo I had that and the guests were making positive comments. I'll run a little experiment on these later tonight.
Added 8/17
Set the show tank at different heights, with the top from ground level to way up. Used both glass walls and the solid wall. It didn't matter - the guests made the same comment "what a cool trick" no matter how high the wall was. I was really surprised with the solid wall! Having the exhibit tank with the top at the same level as the ground or up high also made no difference in guest comments.
Added 8/20
Ran an experimental show. Had the normal set up with a one-tile path in front of the grandstands. Had another one with no path in front of the grandstands. (The path did come up NEXT to the grandstands). And a 3rd with extra path under the front of the grandstands which I always heard was a big no-no. Well, guests entered the grandstands in all cases! No hacks or used items in place.