At that size, it's hard to tell on the morey species, but keep your fingers crossed it's NOT a green morey as these commonly reach in excess of 7' in a surprisingly short time.
We have a green wolf eel, a snowflake morey (specialized crustacean feeder) and an ocellated morey all getting along well in our 300 gal. tank, along with 4 volitans lions, a 6-lined soapfish/grouper and a few others.
Occassionally, the wolf eel (actually a relative of the dottybacks and not a true eel) will cop an attitude and flag in front of one of the moreys, but he usually subsists and soon they're all back to getting along again.
We recently caught a small unidientified eel that we now think is one of the congers, but only time will tell whether he's a juvenile or a dwarf species, so he's in a more peaceful community tank for now.