The Pygopristis Denticulata is not as aggressive as most other piranhas but will eat anything. its family is serrasalmidae but its genus is pygopristis, from what i know its teeth are much smaller and finer than those of the more aggressive piranhas. That having said it is not a good idea to hand feed this one either, it is capable of some painful bites if cornered, which obviously would happen in the aquarium, unless its round ofcourse;) Your biggest challenge is obtaining one anyway