I've been to several - I find them fascinating! There was one on Sentosa, a small island off Singapore, which was fabulous. I spent a long time sitting on a bench there, getting mildly hypnotised watching the fish swimming around above me. There is also one on the coast near me here in England, at a place called Tynemouth, which we go to quite a lot with our son. As well as the fish tunnels, they have seals and other sea wildlife that he loves to watch. And we frequented an aquarium in Brussels too.
Some years ago we went to the melbourne Acquarium and only a three weeks ago we visited Reef HQ, the coral reef acquarium in Townsville. There was a fantastic dive show, a discovery pond for the kids, (the big kids as well) and the tunnel where fish surrounded us. A great day out.
Yes, many years ago, I took 2 of my nieces to the Darling Harbour aquarium, while they were visiting Sydney from Oodnadatta, S,A,, & my husband & I took our eldest grand-daughter to the Melbourne aquarium 2 years ago.