Try and convince an 11yr old to kill his 2 favourite fish.
I'm with cowbla 1 on this. You couldn't get me to kill an animal because of what might happen to it in the future. If I couldn't keep it myself, I'd at least try to make it available to someone else who could.
This sounds too much like the way some people kill kittens when they grow up and become cats.

Not being cute is hardly a reason to put a living creature to death.
I'm sure that, with all he's learned already, cowbla will make a much better choice the next time he stocks his tank.