On the topic of will more protein and less food raise bigger fish cheaper. I would like to add that the effect of higher or lower protein would also depend on the species of fish. Take ML's talapia that are eating algae but growing though that is not a source substantially high in protein. If ML ran out of algae and fed bread the tilapia would probably still grow quicker with the additional food source, though low in protein. Now the purpose of the Tilapia is to grow and provide a high protein source for the LMB in ML's experimental pond. So would higher protein and less food be as effective would depend on the targeted species and subsequent purpose. Many fish have the characteristics of land animals ie. dogs need protein to grow but cows can grow on grass, the point being the benefit of higher protein may depend on the purpose of the feeding program.

Don