Fire eels are not aggresive towards other fish 'cept con specific ime.. and they are nasty towards other "eels".. They leave other fish alone. But Jar's are notorious aggressive fish.. if it was simply the dats and the PB.. and they where small enough not to do harm, and not to small to eat. I would say with plenty of hidieng spots you liekly won't have an issue.. But.. Jar's... eh.. fire eels don't have much for protection. It might work with a good amount of PVC/driftwood for the eel to hide in. but you'de likely never see it due to hiding from the Jar. If the Jar is non-aggressive towards the other fish.. I would say It may work. never had a Jar.
Lots of PVC pipes, driftwood for the Eel if you're gonna try it.