sucking fish vs suckerfish

sucking fish and suckerfish both are nouns.

Word	Noun	Adjective	Verb	Adverb
sucking fish	Yes	No	No	No
suckerfish	Yes	No	No	No

As nouns, sucking fish and suckerfish are synonyms defined as:

sucking fish and suckerfish: marine fishes with a flattened elongated body and a sucking disk on the head for attaching to large fish or moving objects

Other synonyms of sucking fish include remora.

sucking fish (noun)	suckerfish (noun)
marine fishes with a flattened elongated body and a sucking disk on the head for attaching to large fish or moving objects	marine fishes with a flattened elongated body and a sucking disk on the head for attaching to large fish or moving objects