spiny eel?

I have a standard 55g tank and have a P. Del, P. Buet, and a P. Sen. I was wondering if there was an eel that would be fine in there. I really want a fire eel but I already know that it would last in there long term, and I wouldn't be able to upgrade fast enough to accommodate one. Just looking for a spiny eel that wont get eaten by my sen because he is voracious and quite evil. I have another 55 that I could put one in to grow him out but eventually would want him in with the bichirs.