The plural of aquarium is aquariums or aquaria.
An aquarium is a transparent tank or vivarium that is used to house and display aquatic plants and animals, typically fish. Aquariums are created for recreational and educational purposes, allowing people to observe and appreciate marine life in a controlled environment.
The graph shows the occurances of the plural of aquarium in written English since 1800 using Google's Ngram Viewer.
Sources:
https://www.collinsdictionary.com/dictionary/english/aquarium