sandfish vs percoid

sandfish and percoid both are nouns.

Word	Noun	Adjective	Verb	Adverb
sandfish	Yes	No	No	No
percoid	Yes	No	No	No

As nouns, percoid is a hypernym of sandfish; that is, percoid is a word with a broader meaning than sandfish:

sandfish: either of two small silvery scaleless fishes of the northern Pacific that burrow into sand
percoid: any of numerous spiny-finned fishes of the order Perciformes

Other hypernyms of sandfish include percoid fish, percoidean.

sandfish (noun)	percoid (noun)
either of two small silvery scaleless fishes of the northern Pacific that burrow into sand	any of numerous spiny-finned fishes of the order Perciformes
fish of sandy areas of western Pacific and Indian oceans having an angular snout for burrowing into sand