a ternetzi is a different variant of the red bellied piranha (from peru i believe? I could be wrong though) it grows slightly larger than the typical red bellied piranha and has a yellow belly instead of a red belly.
Let's just say i've been able to visit them (not even in a display tank) for 3 years now so i doubt they're going anywhere anytime soon. All the smaller ones have sold.
ternz are nice fish, everyone who had them said that they are fun as compare to the common rbps you see in every lfs.
for your viewing pleasure http://opefe.com/nattereri_2.html