Gflo its never a waste to have questions asked. You have ask a very good one. I will do some checking. One point I note is you addressed one side of the growth question - energy in. The energy out (used) part is equally as important and furnishes the demand side of the equation for energy in. It’s not only a digestive function but also a metabolism question. Keep in mind that unlike many livestock type animals most fish are cold blooded and their energy demand slows greatly in cold conditions where as in warm blooded animals it increases to keep body temps up. This effects digestion and energy demand as well as other biological functions.

Another thought is the comparison of fish feed to live fish and other forage. While feeds are good and live forages have different nutrient results (not all forages are equal or the same) I don't think that feeds offer as much as live forage for growth. The best feeds are designed by doing an analysis of live prey (optimum diet) and trying to match them. They are good but not quite as good as the real thing. That is the main reason that the major ingredient in better feeds is fish meal and oil mostly from menhaden. These comments are for predator fish (LMB , HSB , BG , YP , trout etc) and there is some difference as to the omnivore types ( catfish and GShiners ) and even more difference as to the herbivore types (tilapia , shad , carp etc) at least as to the diet requirements for feed vs. live forage. Not all fish need more protein or fish as a source. That is one reason for the different types of feed. More later.