if the feeders are sickly, wouldn't you expect the predatory fish to be sick as well, since the same people and equipment is in use in the store?
I know that feeders are bad from my friends experience, massive ick breakout.
Each generation imagines itself to be more intelligent than the one that went before it, and wiser than the one that comes after it.
It is not the strongest of the species that survives, nor the most intelligent that survives. It is the one that is the most adaptable to change.