When I was importing into Florida, the best Moorish idols came from Hawaii. They would eat flake foods within a day or 2 of arrival. The nicer looking ones were coming in from Bali but because of the distance, they were in bags for longer periods of time which took their toll on them so I stopped bringing them in from anywhere but Hawaii. That being said, the fish , in general, is a more difficult fish to keep in an aquarium. They do better in schools than as individuals and and have been know to.. (and I quote my friend, the late Dick Boyd) " flake out for no reason." ( He kept a school of 20 in his 1,000 gal
tank.) They need space, and lots of it. They can also be belligerent to other fish in the tank as well. Make sure you feed both meat AND vegetation if you get them.
B&W Henniochus used to be called ( and maybe still are) "Poor Man's Moorish Idols". The biggest difference is that they tend to be a hardier fish and less expensive. Some of the hennis are not as hardy as the H. acuminatus however so you need to be specific when you say Heniochus. We treated them like Butterflies with much success. Varied diet, open swimming area, no tankmates to chew their dorsal fins, etc. worked best.
Hope this helps