I woke up yesterday to find that the New Eel that I introduced into the situation had bitten the older one really bad. Serrations along the whole midsection, but no blood.
At any rate, I'm not taking any chances so I corralled the older one to one side and put in a makeshift divider made out of egg crate. It's working so far ... I plan to let them talk through the bars for a month or so, and then I will remove the divider. If the fighting starts up again, then I'll have no choice but to take one of them out and adopt it out.
The bigger eel seems like the female though, because she is so violent and has to be in control at all times. No insult intended ladies...