Highly doubtful. It's always possible, stranger things have happened, but I definitely doubt it. Banggai cardinals are not known to eat small fish. They are really only aggressive to other cardinals (PJs and Banggais)
The best way to get banggai cardinals to eat is not neccessarily with fry, but with brine shrimp/ghost shrimp and then a mix of mysis shrimp. This is much more natural than eating small fish.