I was quite impressed with Ripley's Aquarium, I thought it'd just be a few aquariums here and there but it was quite extensive. I especially liked the conveyor belt where you can just stand and watch a whole bunch of different sharks swim by.
I would suggest going on a weekday if you can as it gets quite busy and some parts you can't get that close to read the info or look at the odd fishes.
I also liked that near the jelly fishes there was a sitting area to chill out and zone out.
Towards the end of the conveyor belt, it feels like the tour ends, but you actually get to keep on going for a bit for some more aquarium fun!