Two pics, one of each.
View attachment 1065361View attachment 1065362
I'll create the thread concerning my other piranhas later.
Those are beautiful!
I would not risk it - I would understand if they were easily replaceable - hate to say it, but true. But why risk one or both of your prize fish? It's not like having them together will make them any nicer.
I would set up two tanks beautifully - one for each, and enjoy. Twice the pleasure, in fact.

They shoal. George had a pack of good size fish together for a long time in his store. I guess nobody could afford them at the time, peak of the recession. I estimate it was a 6 ft tank.
I'd say try in a bigger tank. I wouldn't go smaller than 6ft.
Sent from my iPhone using MonsterAquariaNetwork app
But it's too late to buy the last one.