I think I can offer a little bit of help since you haven't received any other replies.
First of all, um, you really shouldn't keep a scopas tang in a 55. I know there are those that do and they say there's no problem. But, if you are really interested in maintaining a saltwater aquarium then you obviously have an interest in the animals you wish to keep. And in order for you to maintain that interest you will need to learn respect for those species. Sooner or later, hopefully sooner, you will begin to respect the Scopas Tang and you will realize that a 55 gal drop shouldn't contain a species that has evolved in an ecosphere that is just a bit bigger than that.
I know I've dragged on and I apologize if you feel as if I am flaming you. We've all learned our lessons, most of us have learned them the hard way. That's why we try to pass a little bit of wisdom onto someone else.
In terms of feeding. I wouldn't limit the amount of food you provide the lionfish. He should feed to saturation 2-3 times per week. That doesn't mean you should feed until he looks like a softball. But, you should feed until he is full. The same goes with the eel. The snowflake eel will tell you when he is full by refusing to eat anymore food.
Additionally, it is much healthier for your fish if you provide a varied diet. Try feeding coctail shrimp or chunks of whitefish. You may even soak some of the silversides in a vitamin to help supplement their diet.
Overall, good luck and don't stop learning about that amazing ecosystem.
