I realize I am chiming in later, but A) fried salmon skin is used in sushi, and it is awesome. It is. it is crispy but delicious because they use pieces with a bit of fat. B) I don't recommend feeding fresh water fish any fish that spends part of its time in fresh water because risk of parasites being transmitted are much higher. If you want to feed them fresh seafood, go with prawns, or sushi grade salt water fish like albacore. As for the prawns, only buy from the butcher, don't buy the pre sealed stuff, cause it has chemicals in it that can be bad for your fish.