IMHO,a 30 gallon or larger aquarium with numerous hiding places is suitable for the lion..as the lion will hide while acclimating to its new environment..so as not to stress it out..
When first introduced into the aquarium, live saltwater feeder shrimp should be used to entice this fish to eat. The Dwarf Lionfish diet consists of meaty foods such as live shrimp (including ornamental shrimp), live fish, and sometimes, crustacean flesh.
Just My $0.02