The most important fact is that fish digestive systems are designed to handle certain proteins. Freshwater/Marine proteins and fats are very different than their mammal counterparts. Their digestive systems are well designed so that if the food is of a protein that can not be digested properly it will simply be expell this excess immediately. The primarily function of breaking down food is a provide energy, that which can't be processed generates a lot of waste since they're expelling what can't be used to benefit the fishes body. Proteins are made of amino acids which contain nitrogen, carbon, hydrogen, and oxygen, so as the fish is breaking these non-native foods down they in turn make a lot more nitrogenous waste which as everyone knows will effect water quality. The last issue I have is the fish's kidneys and liver work harder than they would have trying to process foods they are not designed to digest, where as long term feeding can lead to liver or kidney failure. So not to ramble on any longer I can't see any benefits to feeding beefheart/chicken liver when there so many healthier choices such as salmon, nightcrawlers, shrimp(prawns), and prepared pellets.
