I concur with what everyone else is saying - snowflake may do okay in there in the time you have left, but if you add anything fish-wise, you're basically telling the eel that it's lunch time.
You COULD export the eel now, while it's still alive and healthy, and pick up a couple of nano fish. In the end I think you'll find they're more entertaining to watch, easier to keep happy, and will give you more of the "saltwater experience" that you're looking for.
Just my suggestion, of course, and no offense intended - but there are some animals, no matter how young, that just wont thrive in an aquarium that size. Eels are one of them.
firefish, ocellaris clown fish
caulastrea, green star polyps, palythoa, zoas