Katree
Technically, there is no such thing as a freshwater lobster. I've bred crayfish for a long time, and have never fed mine with live fish. They seem to be like cats. Some hunt and kill rats and mice, but others do not. I know it's not a perfect analogy, as cats are taught to do so, while some crayfish may never hunt fish.
I've used sinking pellets, even rabbit food, to feed my crays. As a treat I give crays, and larger shrimp, blanched veggies, such as peas. I also occasionally feed them small chunks of tuna (packed in water, not oil). I've heard of others that feed red meat, but this is risky. Red meat can foul the water if not strictly monitored.