No, Morays aren't solitary. They're fine with anything too big to eat, which can be a task, as it's hard to visualize what they can or can't eat and where they draw the line at too big to eat. I had some Mono Sebaes in a salt tank with Mr Nibblez my Hawaii Dragon and the only one he didn't get down was over 8" tall, but was still killed in the process of trying. However, Mr Nibblez is a hook jawed fish eater so he (it) is much different then the Polyuranadons. These Polyuranadons have more typical Moray mouths catered to smashing as well as spearing so they're a bit more predictable, but I'm sure will still cause damage trying to eat fish.
I can't find the pic....... Jojo (Ichibahnasiatropical) had one that was supposed to be like 2-2.5'
I know I've gotten a pic from Wes of an adult, but having trouble finding it......