The yellow tang, also known as the lemon sailfin, yellow sailfin tang or somber surgeonfish, is a species of marine ray-finned fish belonging to the family Acanthuridae which includes the surgeonfishes, unicornfishes and tangs. It is one of the most popular marine aquarium fish. It is bright yellow in color, and it lives in reefs. The yellow tang spawn around a full moon. The yellow tang eats algae. The yellow tang has a white barb, located just before the tail fin, to protect itself.

The sailfin tang, the Pacific sailfin tang, purple sailfinned tang or sailfin surgeonfish, is a marine ray-finned fish belonging to the family Acanthuridae which includes the surgeonfishes, unicornfishes and tangs. This fish is found in the Pacific Ocean and is popular in the aquarium hobby.