I can't disagree with that. The Aquarium in good conditions can be a magical dive, shallow with enormous numbers of brightly coloured fish and other critters. I have however dived it when conditions were less than stellar and then it wasn't that great.
For me the best dive in that area, probably the best dive I know anywhere in Belize, is Half Moon Caye Wall. A most superb wall dive along a near-vertical wall of corals and sponges, with the open sea a deep blue. I spend a lot of my time on that dive looking out into the blue for sights of mantas, spotted eagle rays, large sharks and turtles. Again, I have done the dive in cloudy murky conditions and it is still a good dive.