In my personal opinion, I will always advise against attempting to keep these fish until their natural diet (sponges, tunicates, etc.) is able to be provided in substantial quantities in a captive environment. Yes, there are a <u>few</u> cases where Moorish Idols have been able to survive for a longer period of time in captivity than expected - due to an adaptation to more common foods - but such anomalies are so rare that I do not see the point in gambling with the animals' lives. Again, this is just my humble viewpoint, though.