Carole, these butterflies settle in very well and feed quickly in captivity as is common with most planktivores. I regularly see them each year when I travel to Hawaii and Micronesia, and they shoal in large groups high up off of the reef feeding on plankton. There is a close relative to this fish, Hemitaurichthys zoster, that is found in the Indian Ocean and fairly attractive. The other members of the genus are quite bland and therefore not collected. Some of the well known online places will get them from time to time...
Devilboy, when you dd them to the tank is not to critical, as they settle in well, are not aggressive, and can take a beating fairly well compared to other butterflies...