feeding live isn't the best choice if you are concerned about nutritional needs. the fat content in commonly used feeders (goldfish, rosies, guppies) is extremely high when compared to your marine fish. this can lead to an early death caused by organ favor due to fatty degeneration.
a better choice, in my opinion is to find a grocer that sells meaty seafood such as: squid, clam, shrimp, etc. silversides are also used with success for marine carnivores.