Bang Guy is correct. Feeding live fish will lead to fat deposits on vital organs (liver) and they can introduce pathogens unknown to your saltwater specimens that can cause disease. Lionfish are usually quite easy to break from live foods. All it takes is patients and a feeding stick (usually clear acrylic.) Once you get them on prepared foods, it is super easy to feed them. The only lion I kept ate squid, silversides, krill, clam, etc. Good luck.