I've sometimes give my bichirs Occidozyga laevis or Paddy frogs but they're kinda expensive and the bichirs have a hard time catching them since they float.
several lfs i've chatted with who have huge bichirs claim tht their secret is bullfrogs. so i would think it's a good addition to any bichir diet. even then you should still ensure the fishes recieve a balanced diet!
