I had a snowflake with a ghost ribbon eel--until the ghost eel showed up with a bite sized chunk of its long dorsal fin missing. The snowflake went to the local pet store, and the dorsal fin on my ghost eel grew back. He is much happier now that he does not have to hide from the snowflake and is out and about all the time--gorgeous.
I would be very careful with the banana--very expensive fish to play around with --- my ribbon was not very aggressive and I don't know about the aggression level of a banana
Of course the lfs told me my ghost would be ok with snowflake, but they were wrong......