I thought you were kidding at first.
What are the dimensions of the tank? I was under the impression it was really tiny. I have no experience with ribbon eels but I thought it was still true that these guys still have a very high mortality in the hobby. If you've had one before then you know the score with them better than I do.
Myself having tried a different species of eel (golden dwarf in my case) in both a small setup and a larger setup, the one in the smaller tank wasn't quite as comfortable in his surroundings as the one in my cube tank. For an animal which you can tell is functionally blind at the best of times, he's surprisingly spatially aware.
So anyhow I would probably steer myself away from a ribbon eel at the best of times never mind one a nano, but what I know is only based on hearsay, and I do remember that you had one before and was able to train him onto food.