Still Enjoying Manga

Futari wa PreCure: In episode 11, Honoka (Cure White) and Nagisa (Cure Black) take Nagisa's little brother Ryouta to Tokyo Sea Life Park.

Doki Doki! PreCure: Episode 1 is set in Tokyo Clover Tower, obviously based on Tokyo Skytree, and it seems to have an aquarium in part of it, but it's only in the background of a scene.

Go! Princess PreCure: In episode 36 the Cures meet Asuka, a vet (and doctor of marine biology). Asuka is impressed that Minami (Cure Mermaid) is friends with Tina, a wild dolphin. Asuka has come to pay a visit to an aquarium owned by Minami's family and the gang go to watch her work. Minami in particular finds herself inspired by Asuka. In the final episode of the season, Minami is shown going to work as Asuka's assistant.

Healin' Good PreCure: In episode 5, Nodoka (Cure Grace), Chiyu (Cure Fontaine) and Hinata (Cure Sparkle) go to an aquarium together. The episode is an opportunity for Chiyu and Hinata to become friends.

Tropical-Rouge! PreCure: The premise of this season is that Manatsu (Cure Summer) moves to a city to live with her mother, who works at an aquarium, so it appears in multiple episodes, including episode 1. In episode 3, Manatsu takes some of her friends to the aquarium, including Sango (Cure Coral). The aquarium is most prominently featured in episode 27, when the Cures visit it hoping to enjoy a dolphin petting corner, but the villains are targeting the aquarium.

In episode 36, Minami (Cure Mermaid) meets a marine vet called Asuka and watches her work at an aquarium. Later that day, at a party on a cruise ship, Asuka half-jokingly suggests Minami come to work with her. In episode 45, they have a conversation in the aquarium in which Minami tells Asuka that Asuka has helped her remember her dream of understanding the oceans through the creatures in them. At the end of the series, Minami is shown going to work as Asuka's assistant.