The Blue Diamond Piranha is a (Serrasalmus Rhombues) also known as a Black Piranha, actually a (serrasalmus Rhombues Complex) the only difference in a Blue Diamond and a regular Black Piranha is the body has large blue scales on it, It almost looks like one sprinkled blue gliter all over its body.
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.
Red eyes. No clear terminal band (hyaline edge) on tail fin.
Blue Diamond Piranha Juveniles and sub-adults can be kept in a tank measuring 32x14". Adult Blue Diamond Piranha 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 Piranha's can be very shy. Therefore, they need a well planted tank with driftwood or rocks to provide shelter. When larger, this species becomes very agressive, and places to hide are no longer really necessary.
NONE. Blue Diamond piranhas must be kept in thier own tank due to their super aggressive nature. They make a beautiful show speciman. It is a beautiful site to see the light reflect off their Blue body when they are swimming in a well lit tank.
This species will accept all common food items, like fish (fillets, frozen fish and live feeders), shrimp and other crustaceans, insects and, when large enough, mammals, reptiles and amphibians.
In the wild, Blue Diamond Piranhas are parasitic fin nippers when young, full blown predatory carnivore when older. Will, almost without exception, not tolerate anything else living in its tank. Even much larger fish will be attacked, nipped and injured over and over, until they finally perish.
(Picture above is of a subadult already starting to show color)
Comments: Blue Diamond Piranhas are actually a Serrasalmus Rhombeus complex.
This large, and very powerful species of piranha is not considered dangerous to man in its wild state, but it can deliver extremely painful wounds. It is said that a mature S. Rhombeus is capable of severing a man's hand at the wrist in two or three bites, and given the potential size of this large and very powerful species, it's hard to believe this is a gross exaggeration.
When we are talking about the Rhombeus Piranha, we are actually referring to a complex of several different forms and closely knit species of fish, all with slightly different habits and appearences. Some varieties are the Xingù, Highback, Blue Diamond, Gold Diamond, Black Diamond, and Jet Black Rhombeus. Due to their highly intolerant behavior, these fish should be kept solitary, and are best suited to large display aquariums.