I am more in the camp of: variety is the spice of life and, a little of what you love won’t do you any harm.One of the easiest to understand and best (I think) food philosophies for people is simple statement "Don't eat anything your ancestor (caveman) wouldn't recognize as food."This is recognizing that humans are omnivores and hunter-gatherers; none of these fad diets and weird s**t.
While I try to eat by this, I do have a weakness for dark chocolate.....
I think that can be translated into chicken feeding. For mine the ‘variety’ comes mainly from their pasture field which is for sure not a monoculture but does not have fish, and the ‘little of what you love’ is mainly in the form of shrimp heads/tails, melon guts, cheese and sometimes meat.
The alternative choice is an uncrustables frozen & thawed pb&j “sandwich”. No water is available with lunch. And the kids have to take milk even if they don’t want it (there is no non-dairy alternative available for those that cannot or do not want milk.) Breakfast is even worse. “Whole grain” cereal (like Cocoa Puffs or Cinnamon Toast Crunch), a cheese stick (I kid you not, they are given at every breakfast), and a piece of fruit *or* “fruit” juice, plus of course a carton of milk for the cereal. There is a table for all the kids who take the required fruit and don’t want it. Other kids can take a second fruit but usually there are a bunch unclaimed. Technically the fruit is supposed to be thrown out if not eaten, but our manager will save me the fruit to offer in my class as long as I am quiet about it so she doesn’t get in trouble. Most of the kids in my building (prob 80-90%), are below poverty line and get the free government provided balanced breakfast & lunch.
some parents add candy that the children may eat after the sandwich. But hopefully this has changed now. At work there are more snd more people bringing salads and other health food. 
shame I'm looking this stuff up while seated in a restaurant, I nearly choked on m garlic bread!!
