The game was first released in 1998 on the PlayStation exclusively in Japan as Theme Aquarium, part of the "Theme" series of games by Bullfrog Productions. However, when it was released in 2000 for the PC exclusively in Europe, it was simply titled Aquarium with the "Theme" name and any mentions of Bullfrog Productions dropped.

The reason for the PlayStation version featuring the "Theme" brand was that the previous Theme games had proved popular in Japan so publisher EA Square wanted to help further generate interest by asking Bullfrog to use it in its marketing. When porting it to the PC for the West, the reason to simply release it as Aquarium was due to the belief that "the game quality wasn't high enough for it it come out in the West as a Theme game, with the Bullfrog brand," according to Shintaro Kanaoya, who provided localization assistance.