Ever wonder why tangs are also called surgeonfish? Well, if you take a close look at a tang’s caudal peduncle, the narrow part of the fish that separates the caudal fin (or tail fin) from the rest of its body, there is a sharp blade-like appendage. This blade is either hidden or exposed depending on the species, but in either case it serves as a formidable weapon against possible attackers and as a display during times of con-specific sparring, such as times of mating. Some fish have very pronounced blades, like the Naso tangs that have two large blades on either side of their bodies, while others have little to no visible blade. And yes, those blades can be very sharp and will cut your skin if a tang in your aquarium decides to be a bit too aggressive.