I think I'm probably the one whose post you read about the eel not eating when I tried to bring up his salinity.
He still lives in lightly brackish conditions, and I use marine salt, not aquarium salt.
He started out life (before I educated myself) living with an oscar, about 4", a pleco and various other fish. The eel was about 6". It took about 6 months, but the eel killed the oscar - and every other fish in the tank. He ATE the pleco, spiny armor and all. That eel has killed any and every fish ever put in his tank. The fish he cant eat, he maims and they die anyway. He once cleanly beheaded a 6" tinfoil barb (the fishstore owner assured me they'd be too fast for him to catch. Again, this was before I knew I should be adding salt to the water). The list of fatalities include, but are not limited to: oscar, convict, pleco, tinfoil barbs, silver dollars and as I started aclimating to brackish, monos, scats and archerfish. None of these fish, save for the pleco were small enough to fit in his mouth.
He now resides in an 84 gal, by himself, save for a colony of feeder guppies. He's nearly two feet long, and I've had him for about 3 years.
As I remember, he started eating ghost shrimp right away. To make sure he was eating, I would catch the ghostshrimp out of the bag with a pair of tongs (I still use those to feed him) by the tail and hold them next to his mouth until he snapped them up. I'd usually give him about 5 or so, and then let the rest go in the tank for him to hunt down later.
Eventually I was able to get him started on dead food (go to your local grocery store, and buy various bits of fish from the seafood counter) with the tongs as well, as he associated food with seeing the tongs. Now he eats his resident feeder guppies, dried and/or frozen shrimp and krill, shrimp pellets and occasional seafood counter treats like scallops, mussel, catfish bits ect.
Do NOT hand feed them. It HURTS when they bite you.
I doubt you'll have any luck keeping yours with other fish if it survives. (Most of them die before they ever start eating.) It'll kill them. If you decide to try it, I hope you choose fish you're not fond of or at least aren't very expensive.
Good luck either way.
Zek