Well, I guess it depends on the tenacity of the eel. But in general, anything that seems small enough to be eaten (bite size) will be eaten during a midnight murrauding.
You want to keep your eel well fed.
Some fish to consider
Large angels -- purchase at a good size to start with 6" or more
Big Rabbit Fish
Less Agressive Triggers (Niger, Blue throat, Pink Tail, Etc)
Larger Puffers (Mappa or Porcupine)
Miniatus or Panther Grouper (I prefer the Miniatus for its color)
Bigger Tangs like a decent sized Hippo Tang
You get the idea. 200 gallons is a good deal of real estate to start with. Providing a decent amount of rock (cover) and feeding routinely will keep an eel satisfied and reduce the chance of chowing down on a tank mate. Getting fish that are tough, big, or have a built in defense mechanism like a puffer allows you to build a community around an eel.
where's me money