Your tank, a 46 bow, isn't that large so even a small dwarf eel is going to put an additional bio-load on the tank. Make sure you have a good protein skimmer otherwise you're going to see an increase in nitrates and a decrease in water quailty.
Gymnothorax melatremus is the best eel to get, as they only get to about 12". They're wouldn't bother you corals, fish or inverts, so they're pretty reef safe. They're expensive, usually in the $200-$350 range. You could also try a small Snow Flake eel, though it will grow large in time. They're also may eat small fish and inverts.