I'll second what Jason said, and add a couple things.
Majestics do not ship particularly well, and can be hard to acclimate. Often difficult to get eating, although those that survive eventually take most foods. Because of the difficulty in shipping and acclimating (and I believe the fair possibility of cyanide on these), this is a species where it is well worth the extra to get one from a "premium" dealer like Marine Center unless you have a very good LFS. Buy with care.
As Jason says, they are somewhat shy. If they are bullied at feeding time they won't eat. When happy, they are pigs. Make sure it has plenty of potential hiding places or you'll never see it. Colors often fade somewhat in captivity. Feed a varied diet.
I kept a medium sized one (~4") in a 55 for a year (lost to a power outage) and it was fine, but I agree with Jason on tank size, really should be bigger. This was a full reef, and it never bothered anything, although it did keep the Coral Beauty in line.
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fwiw, imo, ime, ymmv, etc.
[This message has been edited by Gannet (edited 21 February 2000).]