The silver ollar (Metynnis argenteus) is a tropical fish belonging to the Characidae family which is closely related to piranha and pacú. Originating in the Tapajós River basin in South America, this somewhat round-shaped silver fish with slight red-tinged anal fin is mostly found in tanks kept by fish-keeping hobbyists. It will grow to a maximum length of 14 centimeters (5.5 inches).