Great question.
I'm not sure.
I think that a particular food may have "cues" that tell a fish to stop eating.
I also think that how much a fish "likes" a particular feed may dictate whether it will come to the surface in borderline temperatures--like in the 50-55 F degree range. Most of this is speculation, but when fish that start out all the same, and are grown in identical tanks with identical water and identical temperatures, and you've got fish in one tank hammering pellets off the top in 52 degree water, and fish in the other tank just barely blipping the pellets, maybe you're on to something.
If I could just get into their teeny-tiny minds maybe I could know for sure.
One thing I do know is that high quality feeds make bluegill grow a lot, even in really cool water.
Perhaps it would be informative to to switch feeds for the fish (or strains of fish) and see if Mr. Finicky started hogging out when put on the super mystery feed.
Although you might just run into the feed change problem Eric and I discussed above.
