Looks like fairly common melanism that some clowns show as they age.
You can read about it
here.
This is a short "snip it"
Quote:
|
Originally Posted by ANEMONE FISHES AND THEIR HOST SEA ANEMONES
COLOUR VARIATION
The colour of anemonefish of one species sometimes varies. Geographic variation is most common among widely distributed species. For example, A. clarkii, which has the broadest distribution of any anemonefish, is exceedingly variable over its range. Another type of variation is melanism (black pigmentation), which is somehow induced by the host anemone. This topic is discussed in more detail in Chapter 5.
Other categories of variation are related to sex (see Chapter 4), are due to hybridisation, or are purely random. Hybrid crosses between closely related species have been produced in aquarium conditions, and at least one probable cross, involving A. chrysopterus and A. leucokranos, has been observed by us in Papua New Guinea. The most common sort of random variation involves irregularities in the shape of the white bars displayed by most species, particularly the head bar. In some cases, one or more bars may be absent or greatly abbreviated
|
Cheers
Steve