There's not any reason to offer live once the fish is weaned, assuming it gets a good, varied diet. IME, once weaned, fu's become "just another hungry lionfish", and will be right up front "praying to the food god" whenever it sees you.
FWIW, we feed our fishes SW fish flesh (salmon, tuna, cod, snapper, etc), shrimp, mollusks, squid, etc. All of these foods can be had fairly cheaply in small amounts from your local fish market or your grocer's seafood counter. Look for those small 6 oz pieces of fish that are about $4. We're about to bust into some bluefin tuna and yellowtail scraps from by brother's last fishing trip. If you fish, that's a great way to get food.
Feed your fish food items that are about the size of its eye, as they digest better, and the fish prefer smaller bites. There's a correlation between eye size and stomach size on most fishes, so this practice fits right in with that fact. 4-6 eye-sized food items 3x a week is plenty for your fish.