Rhombeus Piranha, Black Piranha, White Piranha, Peruvian Black Piranha, Brazilian Black Piranha, Spotted Piranha, S. Niger Piranha. The Natives call this fish Piranha Preta, meaning Black Piranha, and Piranha Blanco meaning White Piranha.
Very widespread, found in the Amazon Basin, Orinoco Basin, Guyanas, Venezuela, Peru.
At least 45cm. (18"), according to South American locals even as much as 55cm. (22"), and possibly even larger. These claims however still have to be substanciated.
Compared to most other piranha species, there is relatively high number of larger specimen in home and public aquaria (12" and above), although true giants (18"+) are very rare. This species has a notoriously slow growth rate, and specimen of 12" or larger are already really old fish.
It is hard to give an accurate desciption of the Rhombeus Piranha, because it appears in many shape and colour variations (hence people talk about the Rhombeus complex). Besides that, this species undergoes many morphological changes during its lifetime. In general, juveniles have a relatively pointy snout, are silvery in colour and covered with small dark spots. The eyes are silver until they reach a size of about 5-6": then they gradually turn red, until they are a deep ruby red. When S. Rhombeus ages, it gets a more stocky appearance and often a much higher profile (Highback Rhombeus). The coloration slowly becomes darker. This varies from fish to fish though; some become deep black (Jet Black Rhombeus), others turn grey and others gradually get a dirty greyish white coloration. Some specimen have iredescent scales on the flanks, others don't. The same applies to a reddish coloration of the gill plates, throat and fins: absent in some forms, relatively abundant in others. In general, the color of the fins varies from fish to fish as well, and are generally in the same colour as the body. The caudal fin can be as dark as the body itself (in particular in very dark specimen), but it can also be lightly colored, with a dark terminal band and base.
• Red eyes.
• No clear terminal band (hyaline edge) on tail fin.
Juveniles and sub-adults can be kept in a tank measuring 32x14". Adult fish need a tank of at least 60x20x20" (and even more for very large specimen, 12" and more - fish that big are quite rare in captivity however).
Young Rhombeus Piranha's can be very shy. Therefore, they need a well planted tank with bog wood or rocks to provide shelter. When larger, this species becomes very aggressive, and places to hide are no longer really necessary.