This is my experience with a Moorish Idol, which arrived at the LFS I worked at in a shipment they were asked to receive due to weather delays.
It arrived. Owner said: "It will be dead, soon."
Week ended. Moorish idol alive.
Next few weeks, same story.
Moorish Idol eats everything put into the tank...nibbles on LR, brine, any frozen diet sponge based or not, nori, even pellets and flakes.
But owner keeps the mantra: "it will be dead, soon"
Months pass. System crashes. Idol survives. Eats everything. Looks fantastic.
More months pass and one owner of the store realizes, well, heck, might as well design a display around it because this one is a survivor.
Idol put in with Majestic angel. Idol beats the crap out of it, and any other fish put in with it.
Eats like a champ. You name it.
Other owner still says, "it will be dead, soon."
One day, over a year later.
Idol dead.
Sponge diets and all. Contant fresh supply of LR and all. Eating anything and everything. Surviving system crash that took out far tougher fish. Beating the crap out of others. One healthy Idol. Dead, like nearly all the others.
One owner was right.
Please do not get one.