aquarium vs storage tank

aquarium and storage tank both are nouns.

Word	Noun	Adjective	Verb	Adverb
aquarium	Yes	No	No	No
storage tank	Yes	No	No	No

As nouns, storage tank is a hypernym of aquarium; that is, storage tank is a word with a broader meaning than aquarium:

aquarium: a tank or pool or bowl filled with water for keeping live fish and underwater animals
storage tank: a large (usually metallic) vessel for holding gases or liquids

Other hypernyms of aquarium include tank, vivarium.

aquarium (noun)	storage tank (noun)
a tank or pool or bowl filled with water for keeping live fish and underwater animals	a large (usually metallic) vessel for holding gases or liquids