Purina is actually better than Diamond believe it or not. Regular Purina dog chow outranks Diamond in all reviews I've seen. I'm not saying Purina is good, but its better.

I never recommend fish at all in a cat's diet, I'm just giving an example of how a diet based entirely on cooked meat is not the best. This is a very extreme example, but it sometimes takes extremes to get people to take notice and do more research into their pet's food.

There's more to foods than their ingredients tell you. In one of the worst foods I've researched (for ferrets), I found that some of the listed bacteria to aid digestion were actually by-product bacteria from the pharmaceutical industry. More specifically, they were what was left over after culturing and harvesting bacteria to treat yeast infections. Bacteria normally found in certain areas of the human body that don't make for an appealing food additive.