fish bowl vs fish tank

fish bowl and fish tank both are nouns.

Word	Noun	Adjective	Verb	Adverb
fish bowl	Yes	No	No	No
fish tank	Yes	No	No	No

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

fish bowl: a transparent bowl in which small fish are kept
fish tank: a tank or pool or bowl filled with water for keeping live fish and underwater animals

Other hypernyms of fish bowl include aquarium, marine museum, bowl.

fish bowl (noun)	fish tank (noun)
a transparent bowl in which small fish are kept	a tank or pool or bowl filled with water for keeping live fish and underwater animals
a state of affairs in which you have no privacy