cichlid fish vs percoidean

cichlid fish and percoidean both are nouns.

Word	Noun	Adjective	Verb	Adverb
cichlid fish	Yes	No	No	No
percoidean	Yes	No	No	No

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

cichlid fish: freshwater fishes of tropical America and Africa and Asia similar to American sunfishes; some are food fishes; many small ones are popular in aquariums
percoidean: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of cichlid fish include percoid, percoid fish.

cichlid fish (noun)	percoidean (noun)
freshwater fishes of tropical America and Africa and Asia similar to American sunfishes; some are food fishes; many small ones are popular in aquariums	any of numerous spiny-finned fishes of the order Perciformes