[Der_Iron_Chef]

I took this directly from RC:

Clownfish are protandrous hermaphrodites. Clownfish are hatched sexually immature or in other words sexless, neither male or female. This in the simplest of terms means that they change from sexless to male to female. This is a one way trip; sexless to male never to sexless again and male to female never to male again. They may spend their entire life as a sexually immature fish depending on their environment.

For a clownfish to change sex two requirements must be met. First the fish must be physically mature (12-24 months old) and must have an environmental cue to transform. The cue to become a female is the lack of a female in the environment. The cue to become male is that a dominate female is present in the environment, but the environment is lacking a male. The cue to remain sexless is that the environment has an existing dominate female and male pair.