Achilles tangs are definitely not at all easy to keep...one of the "most delicate tangs" group with powder blues, gold rim, etc. Should only be attempted, IMO, in large mature tanks but with no need for a yellow tang! I don't get that one...maybe some scientific thing?!?!?! I just can't figure that one out. I mean, they would eat totally different things in different tanks to begin with...maybe this is an extremely small sample size (the author has one with a yellow, therefor...!). But nonetheless, one of my ultimate favorites.