An old post of mine from years ago .....
To be honest, from a nutritional aspect the average hobbyist typically has no idea what the exact nutrient levels are of the various raw foods that they feed their fish, or how each species will assimilate those various nutrients. You can't simply feed a fish that in the wild is predominantly a frugivore, such as Heros efasciatus, slices of apples & oranges, and assume that this is in any way a more natural form of food for the fish, than a well-balanced pellet. In the wild a frugivore will seek out the fruits & seeds that contain the highest level of protein/fat, not the ones that mostly consist of starch. Add to that the nutrient requirements of most species change as they mature, so what might be ideal for a fry/juvenile, could be (and often is) completely different compared to a mature individual.
The reality is, for the vast majority of ornamental species of fish no one (including myself) has the slightest clue what the optimum dietary requirements are, as the vast majority of these fish have never been studied long term with regards to dietary requirements. Most haven't been studied on even a short term basis. You might be able to mimic a fishes natural feeding behavior by feeding live foods, but most hobbyists will never mimic the seasonal variations of a natural diet that take place in the wild. Raising your own live bearers, fresh water shrimp, crickets, and worms generally won't even come close to matching what a cichlid in the wild consumes on a regular basis. The nutrient profile of each foodstuff is dependent on what each of those foodstuffs in turn consumes, which in captivity is usually nothing remotely close to what those live fish, insects, crustaceans, nymphs & larvae would consume in the wild.
This is why if one refers to the nutrient profile of say an earthworm, one can only ball park that data as the protein/fat/mineral content will be entirely based on the environment of where that worm originated, as in what that worm consumes on a regular basis.
What works best for each species is a bit of a guessing game, which is often only determined from long term experience with that species.