Recently thought about keeping a small eel myself. What you can keep depends on tank size. You will also need a thoroughly escape proof tank, something I'm not sure I can provide
Here is RC's Fish Only & Aggressive Tanks forum. Go back to the "last 100 days" selection at the bottom of the page for lots of posts on eels. Will keep you reading indefinitely
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http://www.reefcentral.com/forums/fo...s=&forumid=139