What species? I have experience with O. Briareus. I have kept 2 in the past and both lived successful lives. The only time one even reached out of the tank was when I teased him with shrimp from above. I had a mesh top and covered the overflow but never did it seem like he tried to get out. People seem to really overdo this one. A wrasse is more likely to get out as they are prone to jumping through say eggcrate.
They usually need live food to get them going. Fiddle crabs are best, but anything live they will go for. Even a small one is more then capable of taking out the hard shelled crabs. Don't expect to see them much for the first few weeks or months. In fact the first one I had I did not see him at all for about a month despite checking out the tank all hours of the night with a red flashlight. This is the main reason you need to feed live, you'll just never see him to fed frozen. Once they get comfortable they become quite social. I played with both of mine frequently.
Keep in mind the lifespan. 1 year is about the most you're going to get. Make sure to get a young one!
If you have more specific questions don't hesitate to ask. I kept them in a 90 gallon fyi.
One day I'll get another but I've since converted the tank to a garden eel tank.