1. Make sure you always have a feeding stick while in the water while feeding regardless of whether your feeding live or frozen so that he associates the stick with food.
2. Then feed him one live and soon afterward one dead on the stick. (I use rosie's for feeders) Wiggle the frozen fish around so that it appears alive, and always offer it head first.
3. The next step is to feed frozen silversides (depending on the size of the lion you may have to dig around in the bag for small feeders). After he takes that your only a few feedings away from tricking him into eating most anything off of the stick.
Ive never seen a lion eat anything off the bottom of the tank that wasnt moving, so dropping the food in the water wont work.
It might take some time, but this method has worked for me with two lions a puffer and a frogfish.