I am glad you can all agree on this. But I might add, in the past every specialist and expert on piranhas has always recommended that piranhas be kept alone as a single specimen or as a group in large aquariums. Large Aquarium meaning Public Aquarium. This mixing of piranhas did not occur in hobbyists tanks on a large scale until a few hobbyists decided to test this theory after I made it known that it was near impossible to do [circa, 1994, 2000].
Since then there have been repeated attempts to force the unnatural. Again, I say to you, these experiments are stressful to the fish. From there you do what you want.