Snakehead vs piranha

Question

Consider this sort of a fantasy aquarium fight club question:

Snake-heads and piranhas are mean fish but if you were to put one of each of equal body weight in the same acquarium, who would be at the top of the food chain?

Info on both fish:

http://en.wikipedia.org/wiki/Snakehead_fish

http://en.wikipedia.org/wiki/Piranha

Answer 1

From what i saw on river monsters, piranhas only attack if the prey is in a distress.

Answer 2

A Black Piranha will destroy any fresh water fish, that's a fact.