Ensure that your moray has a real shelter(s) readily available. I've had eels with & without PVC cave systems & the difference in behavior is dramatic (at least in my experience). I currently have two morays in my 100gal system with a buried PVC cave network in the DSB with multiple entrances hidden within the rockwork. I have had no escape attempts whatsoever. The eels are relaxed, & glide in & out of their chateau at lesure. My hood is now partially open (simple glass panes) & has been since last January without incident.
I used heavy duty lucite prior to this but it slowly warped from the heat of the lights. For smaller eels like the types I have, stock glass enclosures should work fine. I've seen some systems that the lids are actually weighed down.
good luck.