My Eel may be sick, any suggestions?

[TiggertheOscar]

My fire eel, whom I have had for several weeks, appears to have a swollen "back". I say back because it is located more in the upper portion of his body as opposed to the belly area. Note that he was fine when I first got him, and at first I fed him red worms, but they didn't seem to satisfy him, so I went to Nightcrawlers and he was eating 1 a day for about 2 weeks till now. It's been 2 days since he's eatin anything.
This is my prize fish and I would hate to lose him for any reason.
I will try to post a pic when he comes out of his home.
Here are my readings for the tank=
125 Gallon
ammonia:0
nitrites:0
nitrate:15-20

Other fish are 3 Oscar's, a common Pleco, 2 Bala's and a Feather-finned cat.
Filtrarion is 2 biowheel350's and a fluval fx5.
Thanks for your help!

 

[OrangeCones]

Looks bloated in the top picture. Not sure how to help him/her. Peas usually help bloat but hard to get an eel to eat veggies, plus you say its not eating.

 

[TiggertheOscar]

On another forum they advised me to use some epsomsalts, 1 teaspoon for every 5 gallons, so tonite I did a 30% water change and dosed the epsom... We'll see if everyone is crappin their brains out by morning, lol.

 

[TiggertheOscar]

My poor eel has passed away. I feel horrible, as if there was something else I could have done...
I will be replacing him though, I love fire eels.
Does anyone know of a place online or off (in the Chicago area) I can acquire another?
And for future reference, what can I do differently to avoid this from happening again? My oscar's love the company thats for sure, so compatibility is not really an issue. My water parameters were within reason, so it leads me to beleive it was either a pre-existing condition or the nightcrawlers I fed him were the actual cause of death.
Anyone's input is greatly appreciated and thanks again for the advice in the first place.