Young man, you need to make the picks you like and among the members here should be able to assist you on what is ideal from one to the next. Also, if your so dead set on having an eel, their better choices. but still you not can manage so larger of fishes in so small a tank for by having any eel, you right there must give this animal free space as the next choice you make for as these animals grow, they will among themselves become stressful and then you will view on why its a bad idea.
You need to select a number of fish and the larger they grow be the less you can manage in this tank. Do not go by that old ruling of one inch of fish to so many gals of water for as it was said somewhere, that rule is so old and you want to hear something? That rule wasn't around in my beginning years, not until much later.
The problem in the eels you can pick from that even that they grow 2', they still can mange to put the bite on any of their tank mates, so over crowding is out and not so small a fish is out as well. Also, dwarf eels in most could work for you, but I would be concern of your water quality in the aging of your tank for if you can not manage to keep your tanks nitrate levels extremely low, your be having other problems in best in keeping most any eel.
Its always more easier to say I can do this or do that, but doing certain things all the time each and every week for some, sooner or later many look to make short cuts and then, that be all they wrote. With the bio load you are selecting, you would also need to do more often water changes for the week by what I believe would need to be around near to 50%. It is something that is not heard of in the marine world to do a 50% water change but then you your aquarium inhabitants to be concern for your tanks nitrates would go through the roof in no time if you do 12 gals or so for you would have to add so much food in this tank.
I think I`ve said enough, you decide if you listen to the few in here at AC is telling you or the ones in that other forum link that seem to be in some agreement to what you want to do.
I make for a friend of my daughter, her sister who has just started out and I put together for her a list for her to pick from, like I listed four fish, and she could only pick one from those. But mostly, people always want something of their own choice and you should select a few fish that you like most and let other see if they could assist you in few other picks. Also, all the choices I giving this girl, the fish all max out at 3-3 1/2" and she too has a 55.
Buddy