this is pretty much what Oliver and LS said but...
just make sure their are a lot of hiding spots for him to hide in. lots of caves and tunnels. sandy substate (i really like black sand, and if you're getting a snowflake moray eel (which i assume you are based on your tank size) it would look really cool on black substrate. You could lean a large piece of slate against the glass and your eel might choose it as its main hiding spot, so you can view it 24/7. (OF course, this only works if you are willing to have an ugly piece of slate leaning against the front of your aquarium)