We’re not unfamiliar to the sight of “xanthic-koi” type aberrants that plague various fishes. Vitiligo and other forms of patchy off-coloured specimens appear from time to time, and seem to be particularly prevalent in surgeonfish of the genus Ctenochaetus as well as Centropyge. Although we still have no clue what causes this to occur, we know for a fact that this coloration is fluid and mosaics about the body as time goes by. Most of the time the fish loses the koi-colours either completely or partially and revert to wild type coloration, or keeps the aberration but in an ever changing manner.
In most examples, the fish arrive from the wild with partial xanthic coloration or an aberrant koi pattern, and then proceeds to lose it quickly after a few weeks. Few specimens have managed to hold this coloration. Various theories have been put forward by hobbyists, saying that these could be sexual displays in the wild. Others have hypothesised that viruses and other infections have led to the appearance of such mutations.
In rare instances, healthy fish with wild type coloration can develop this phenomenon in captivity. Matt Wandell of Steinhart Aquarium has documented the development of such coloration in previously normal looking fish. The phenomenon appears to be transmittable, although none of the fish showed any adverse health effects.