Serrasalmus rhombeus is a fish of the piranha

Piranha

A piranha or piraña is a member of family Characidae in order Characiformes, an omnivorous freshwater fish that inhabits South American rivers. In Venezuela, they are called caribes...

 family

Family (biology)

In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...

 Characidae

Characidae

The Characidae, characids or characins are a family of freshwater subtropical and tropical fish, belonging to the order Characiformes. The name "characins" is the historical one, but scientists today tend to prefer "characids" to reflect their status as a by and large monophyletic group at family...

 found in South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 in the Amazon

Amazon Basin

The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...

 and Orinoco

Orinoco

The Orinoco is one of the longest rivers in South America at . Its drainage basin, sometimes called the Orinoquia, covers , with 76.3% of it in Venezuela and the remainder in Colombia...

 river basins, the north and eastern Guiana Shield rivers, and northeastern Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

ian coastal rivers. Its length is up to 41.5 cm.

These piranhas live in very diverse habitats ranging from soft blackwater, to hard whitewater areas in the Amazon, and as such, are very tolerant of differing water chemistry.

Names

This fish was long known and traded as Serrasalmus niger. It varies widely across its range and whether it really is a single species is still unknown, though in some cases the fish in question are certainly mere morphs. Peru

Peru

Peru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....

vian S. rhombeus are called jet black highbacks or Peruvian Black Piranhas. Brazilian Black Piranhas are actually greyish in color and some have diamond-shaped scales. Venezuela

Venezuela

Venezuela , officially called the Bolivarian Republic of Venezuela , is a tropical country on the northern coast of South America. It borders Colombia to the west, Guyana to the east, and Brazil to the south...

n S. rhombeus have the brightest red eyes and grey coloration.

Other names include Rhombeus Piranha, for its striking shape. Particularly light-colored populations are the White Piranhas of the aquarium trade, formerly believed to be the "true" S. rhombeus. A common local name is caribe ojo rojo; the species is also known as caribe amarillo, not to be confused with the other "yellow" piranhas S. gibbus and S. spilople.

In the aquarium

It is generally recommended to keep no more than one in captivity, as redeye piranhas generally do not tolerate tankmates, particularly when they are adults. In the wild it is believed that they generally form loose shoals (or schools, but seem to join and leave different shoals at will). Their primary source of food at a juvenile size is the fins and scales of other fish. In captivity it is possible for them to reach a size of up to 14". It is rare to see them at this size, however, as their growth rate is generally very slow. Specimens that are in the upper size ranges can command very steep prices (such as $500 for a 12" fish). In the aquarium they should be fed a varied diet. Many people feed beefheart, and recipes for mixtures abound on the internet. Feeding live food is controversial.

Like all piranha they have razor sharp teeth and powerful jaws and caution should be used when performing tank maintenance, particularly when they are of a mature age. They are much bolder and extremely aggressive at an older age. Juveniles are on average fairly timid. Individual animal temperament does of course vary.

As with any aggressive species, a close attention to water parameters (i.e. ammonia, nitrates) is important, as they are very messy eaters.

All Serrasalmus species are solitary piranhas and S. rhombeus is no exception. They must be kept alone.