Clown tangs are difficult.
Cali Reef use to have one that was a terror but probably one of the few that I've seen that did well in captivity. I've tried a handful of times in the past 20 years and not much success. I now have one from Divers Den, only about 2 months and he only grazes on algae in the tank despite my numerous attempts at all other foods including Reef Frenzy which usually gets to most finicky fish. Just starting grazing on Nori sheets but not a lot of gusto.
So far he's not losing weight, actually maybe gaining a little.
Buying from Divers Den, I know they are only "conditioned" fish but you would think that it was eating with a little more diversity then just algae.