It is something I read often: “Where can I buy a female for my male ____ wrasse?” Or: “I want to buy another ____ wrasse and pair them up!” Wait! Time out for a minute!
First, we really need some understanding of how wrasses interact and live in their natural environment. In the ocean, most genera of wrasses live in harems, which consists of a group of females to one dominant male. Often, there are a few transitional males in this group as well, which are essentially males-in-waiting – waiting for their chance to overtake the current or become the new dominant male. Within this harem, there is an established hierarchy. The hierarchy exists by the dominance of the terminal male and submission of the females and transitional males. It is this last part which is key; there are no bonded or mated relationships. Quite simply, wrasses do not form pairs! Think similar to Anthias here; not like Clownfish.
Now, let us go a step further and explore the female-male aspect. Wrasses are protogynous hermaphrodites. Settled as a juvenile, they all start as female. Females then transition to male in the wild as harem conditions and the environment allow. As females transition, they become a transitional male, or sometimes called a sub-male. At the sub-male phase, a reversal back to female is technically possible and occasionally happens. If the transition progresses, eventually the state of terminal male is reached. It is at this point the process is, in fact, terminal; reversal back to female is not possible.
Essentially, all the females in the harem are continuously attempting to become a transitional and eventually dominant male. It is only the hierarchy, and mostly the current dominant male, who prevent this with overriding behavior. The sub males in the harem wait, until the dominant male perishes or until a sub male can out rival the dominant male when challenged. In many ways, it is a lot like a king on a throne; there cannot be a new king until the old one is removed or leaves the throne. And everyone wants to be king!
In aquaria, it is rather difficult to successfully duplicate nature. All females tend to eventually transition to male, regardless of the presence of a more dominant male. Often, when this occurs in the presence of a dominant male, the new male may end up with best coloration. However, the survival of the old male is always questionable. Sometimes removal of one male becomes necessary for obvious aggression. For these reasons, I no longer bother with more than one wrasse of a single species. I have attempted to keep a male/female pair/trio from the Cirrhilabrus, Halichoeres, and Paracheilinus genera, only to always result in all females turning to male with time. On more than one occasion in both the Cirrhilabrus and Halichoeres genera, I have had males/females spawning with regularity, only for the females to transition to male a few months down the road. It simply is not worth the effort and enduing frustration to attempt these pairs/trios/harems in captivity for the casual reefer.
As an alternative to keeping pairs/trios/harems of wrasses in aquaria, an aquarist may wish to keep single wrasses of each species mixed with others. So long as selections are made carefully, avoiding certain species and in accords with some simple guidelines, the results will be rewarding. Each wrasse is highly likely to eventually transition to male, providing the best coloration. As an added bonus, the hierarchy of the mixed group lends to displays of finnage and “flashing” of colors on frequent occasions for delightful viewing. However, the only catch with this approach is that some patience may be required. If wrasses are purchased as juveniles or females, it may be a while before they transition into males. This time frame is widely variable and depends not only on the fish’s age and maturity but also the hierarchy established amongst the tank mates. The timing is complicated, but it could be as short as a few weeks to as long as many, many months.
So please, don’t try to ‘pair’ your wrasses! At best, it may work for a while, but even in those circumstances time is unfortunately against you. Nature always finds a way!