Well, resurrecting the dead thread but what the heck.
I have a Chocolate mimic tang that's been in my tank for good on 3-4 yrs. I've had him since he was little, but he was never yellow, he has always looked like the adult color morph since I got him. Very pretty fish, pics don't do justice of the colors on these tangs.
I think it may appear that these fish "nip" at corals/clams, but that is not really the case in my experience. My mimic cleans the surface of my clams and some of my corals, but doesn't do any damage to them at all. I'm very hesistant to judge my fish's behavior and have noticed that this type of tang has a tendecy to "clean' various things, especially just after feeding. I actually think this behavior is beneficial to my clams/corals as it rids them of excess detritus, etc.
I just bought a little chronixis today and she is doing very well. I am always amazed at what gutsy little fish mimic tangs are, this gal is only about 2.5" and already making territorial claims against my black/white saddleback clowns that are easily double its size. My chocolate mimic in my other tank is also very aggressive and pound for pound the worst of all my tangs when it comes to introducing new fish.
The chronixis has very round tail fins and it is hard for me to believe that these will completely change as it gets older and it will start looking like a chocolate mimic (if 50% of reports are to be believed). Only time will tell. But this chronixis is SO pretty, the electric blue on the tail is sweet!!
As for availability, my wholesaler gets these guys in at least 10-15 times per year, but the main problem is they are delicate shippers and I think that's why you don't see many at LFS.
Morgan