Japanese required: Moderate (Must be able to speak to get in, the rest of the aquarium does not require Japanese)
Cost: Aquarium is 2000 for adults and high school students, 1000 for elementary to junior high students, 500 for children aged 4 and older. Three attractions and the aquarium costs 2400 for adults and high school students, 1200 for elementary to junior high, and are free for children aged 4 and older.
Good for: Anyone
Every time I've gone to a foreign country, or even a new place in a country, I try to go to the aquarium. Combined with going there once or twice with friends, I've been to the Nagoya Aquarium several times.The Aquarium's split into two parts: a northern building and a southern one. The displays between the two buildings are rather different: the larger animals (dolphins, orcas, beluga whales) are in the northern building while the smaller fish are in the southern building.
I personally never really found the larger animal exhibits to be as interesting as the smaller fish at aquariums. Pretty much every aquarium will have dolphins, so they're not really anything new. One thing in the northern building that would have been extremely interesting to me would have been seeing some beluga whale babies, which was advertised on a sign. I was disappointed when I saw there were no beluga whale babies.
There's also the very common dolphin show, where they make the dolphins spin around in the water, catch frisbees, leap out of the water to touch balls suspended in the air, and the like. It might be worth watching a bit of the dolphin show even if you've seen the show many times to experience the slightly different ambiance of it being in Japanese instead of English. The seating area for the dolphin show is also the most comfortable place in the aquarium, so resting there isn't a bad idea even if you don't plan to watch the show.
The single most interesting exhibit for me was seeing an eel through a tank that had the under-ground portion visible as well. I've seen plenty of eels before, large and small, but I hardly ever get to see how they move their bodies below-ground. Their movements don't really change, but it's still fun to watch an eel swim up and down out of a hole for a few minutes.
The aquarium was quite a bit of fun for about two hours' worth of time. I'd recommend it for people who like dolphin shows, turtles, penguins, small fish, or have kids that they need to entertain for a while.