When I was doing research on this I found some really good information - I'm not sure if I can post a link here but I'll copy the info so you can read it...
Here ya go - hope it helps...
Sexing Clownfishes
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Since there are a large number of posts asking for help in sexing clownfishes or that relate to sexing clownfish I thought I would share some information. This information is both from personal experience and from references from well known clownfish experts.
Q: What is the nature of clownfish in terms of gender?
A: 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.
Q: So what is required for a clownfish to change sex?
A: 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.
Examples of clownfishes sex change.
Multiple clownfish in a group:
When multiple clownfish are together in a group they will form a hierarchy based on dominance. The most dominate fish will become the female. The next most dominate fish will become the male. The rest of the clownfish will have a pecking order but will not mature sexually.
If the female is lost, the male will replace the female. If the male is lost or promoted to female, the next most dominate sexually immature clownfish will become the male.
If by some chance a sexually mature clownfish tries to join the hierarchy it will either be chased off, killed or if it is successful in joining the hierarchy it will replace one of the mated pair by either chasing it off or killing it.
Two clownfish kept together:
If two sexually immature clownfish are kept together they will go through the sex change dance too. The most dominate clownfish will become the female and the other the male.
A Single clownfish kept by it’s self:
If a single clownfish is kept by it’s self it will become a female clownfish.
Q: So how do I tell who is who?
A: In some species of the clownfish it is very easy to tell the female from the male of a mated pair, in others it is nearly, if not impossible. A single fish by it’s self with a few exceptions is almost impossible to tell its gender. Examples of some of the exceptions; maroons, I have never seen or heard of male maroon over 2� long. I have never seen or heard of a A. Ocellaris male over 3.5� long, but I have seen several females that are 3� to 4� long.
The clues: size, color and behavior
Size:Size can be a dead giveaway in some species of clownfish and of no help what so ever in other species. For example maroon clownfish (P. Biaculeatus); most of the time a male maroon will be half or less than half the size of the female of the pair. A typical maroon pairing will have a female of up to 6� and a male that is less than 2�. But in other species like White Snout (A. Mccullochi) and Wide Band (A. Latezonatus) clownfish the male can and often is the same size as the female. In other species the size difference between the smaller male and the larger female is less pronounced, for example Perc’s (A. Percula) , false Perc’s (A. Ocellaris) and Clarkii (A. Clarkii). But keep in mind that clownfishes do not read books or the Internet, and can contradict the known “facts� about them.
Color:
Color can be an indicator of sex, but it is not all that reliable. For example, Maroon clowns (P. Biaculeatus) will both be brightly colored until the female ages, at which time she will get darker in color. The same holds true with Tomato clowns (A. Frenatus). Clarkii (A. Clarkii) clowns are an exception. Many female Clarkii clowns will often have a white caudal (tail) fin, while juveniles and males will have a yellow tail fin.
Behavior:
Female clowns are dominating in the pairing. The submissive clown (the male) will demonstrate his submission by taking a non-offensive posture and exhibit a quiver or shaking motion similar to a seizure. Males tend to be attentive to their females. For example male Maroon clowns (P. Biaculeatus) will “kiss� the cheek spines of their beloved female (this behavior is unique to maroons).
Submissive behavior:
Amphiprion and Premnas species submissive behavior goes something like this… First the dominate fish will rush or otherwise attack the submissive fish. The submissive fish will turn sideways to the dominate fish and tilt its belly towards the dominate fish and quiver like an epileptic seizure. The female should recognize this behavior and stop the attack short of actual damage. Sometimes in new pairings and old well established pair bonds the dominate fish will move to a parallel position to the submissive and quiver back to the submissive fish.
In Premnas species there is an additional submissive behavior that is unique to maroons. When the submissive fish is rushed or otherwise attacked it/he will duck the attack, slip to the side of the female and tenderly kiss her cheek spines and pectoral fins of his beloved female.
The Proof:
The proof is in the pudding or the eggs in this case! When you see your fish lay eggs then you know it is a female. When you see her mate fertilize those eggs you know it is a male. And in the end this maybe the only way to tell which is which in a pair.
Should I be worried? Thanks for any help.
