The Silver Dollar (Metynnis sp.) fish is a South American species closely related to both Piranha and Pacu, and are native to same South American rivers, streams and tributaries. There a number of subspecies of Metynnis who vary in coloration and pattern based on their origins, some common species of Silver Dollar include: Silver dollar (Metynnis argenteus), Striped silver dollar (Metynnis fasciatus), Spotted silver dollar (Metynnis lippincottianus), Red-spot silver dollar (Metynnis luna), Speckled silver dollar (Metynnis maculatus), Black-barred silver dollar (Myleus schomburgkii) and Red hook silver dollar (Myloplus rubripinnis). They have been available within the aquarium hobby since the origins of the hobby, but have remained very popular due to their bright silver coloration, unique rounded body shape and their active schooling swim style. Silver Dollars prefer to swim in medium to large schools and are generally found in the middle to upper regions of the water column within the aquarium. Ideally they should be kept with a minimum of six individuals, which will allow them to school and provide them a sense of security.