I can't recall ever having a problem with them from the eating and they are hardy, but they get big, and they get big fast. They also can have a tendency toward dominance in a tank. Also, in the adult form, they lose the yellow color.
I have a gray which is extremely similar to the french. They are hardy angels with a cool tallish body shape - they do not lose their yellow color - they lose the stripes. Grays lose the yellow.