The main reason most of us keep fish is because we enjoy watching them. They keep us entertained and as with most pets, help make us happy. As pet owners, we want our pets to be not only healthy, but happy as well. A large part of being healthy is being happy or content. I know that conveying emotions to animals is another subject of its own, however, as pet owners we can tell when our pets aren't right (happy), and we try to fix it. As a society we have developed suitable premaid foods for all types of animals, and for that matter people. I would be much happier, and healthier with a nice grilled ribeye or chicken breast, than I would eating a double cheese or mcchicken. Same for my dog. She has no problem eating dog food when she is hungry, but still DROOLS waiting for me to cut her off a chunk of that steak. The same goes for our fish. Sure we can get them to eat flakes and pellets, but never giving them any food that will satisfy their natural cravings is not the way to have a healty, HAPPY fish.
My point, and what I have gleaned from reading all posts till now, is that healthy and happy are conjoined twins that cannot be seperated. There is no way your predatory fish can be 100% healthy eating only flakes and pellets, because your predatory fish is not truly happy. Pellets and flakes are great. They have made it possible for many people to raise and enjoy fish, that would not be able to without them. That being said, if you are able to, feed your fish not only what they need to just survive, feed them what will make them THRIVE. Which, if I'm not mistaken, was the OP's main question.
