I too have a Moorish Idol. I've had him since early December when I bough my (used) tank. I didn't know that he was such a difficult fish to keep but really didn't have a choice really. Previous owner was going to take him to Phoenix (from Columbus) and set him up in a new tank if I didn't take him. I believe he came from a wholesaler in Flordia about a year ago.
I have him in a 120Gal (my next tank will be bigger for him) with a Flagfin Angel, two Blue Green Chromies, a Yellow watchman Goby, two Skunk Cleaner Shrimp, an Emerald Crab, and some Turbo Snails and Hermit Crabs. He is definately the Alpha fish in my tank. He seems to get a long with everyone, but he doesn't hesitate to let them know who is boss. He seems like a very curious, but very stupid fish.
I've even seen him chase the Flagfin once or twice and the flagfin is almost bigger than he is. The Goby is the only one to mess with him, but only when the MI is in his space. About a month ago, I bought some small (maybe too small) occelaris clowns and the MI killed them.

Makes me afraid to add anything else at a later point.
My MI will eat almost anything I throw at it. He seems to have a liking for bubbles though :lol:. I feed Formula One, Formula Two, Brine Flake, Spirulina Flake, Frozen Brine and Frozen "Angel and Butterfly Food." Occasionally we'll put a piece of lettice or spinich in and they like that too. I've heard malnutrition can be a big problem, so I've tried to vary their food as much as I can. I'd like to see about getting him some of the sponge people here are feeding.
Occasionally mine will flash a pale color if he is spooked or stressed. At night he gets pretty pale too. I've tried to include some pictures, but my camera is pretty bad and with the delay its hard to capture pictures when he is zooming all over the tank.
Showing some nice colors here, but its a bad picture.
I accidentally took this one with the flash