James there are a number of things that go into short term growth rate in addition to food. Energetics is a very interesting and complicated aspect of fish biology. I am not saying the higher protein food did not contribute to improved growth but all fish do not need higher protein food. Some need it when young , some all the time and some not at all. In addition the more natural food and the higher quality it is for the species offsets deficiencies in a pelleted diet. A real balancing act.