Weird. I don't recall seeing it in Feb 2009. Chances are it was there, but I'm drawing a blank. I do remember four black-tip reef sharks.
Overall the aquarium was a disappointment. Some nice freshwater tanks for Australian natives and cichlids, but the tropical marine tanks were small, dimly lit, dirty and poorly stocked.
That big tank is built in the shape of a circle - the far side of the circle is not visible to the public (I've heard it is in the owner's living room) so the grouper could have been there when you visited.