Hallo zusammen,
Weil das Thema Lippfische und die damit verbundene Aquarienhaltung sich immer wieder neu erfindet, möchte ich hiermit weitere Kommentare zur Diskussion stellen. Auch die Einschätzung der allseits geschätzten Fossa/Nielsen-Autoren weicht nicht von den hier erwähnten Mustern ab. Von Interesse sollte der Kommentar zum Labroides dimidiatus sein. Nach der landläufigen Meinung über die bekannten Sozialstrukturen der Lippfische läuft diese spezielle Tatsache nicht in der gewohnten Schiene.
Der Abschnitt über den Blaukopf-Lippfisch erklärt in seiner ganzen Deutlichkeit das eigentliche Verhalten dieser Arten. Ausnahmen in dieser Familie sind Paargänger, wie der Napoleon-Lippfisch oder einige vermischte oder lose Haremsverbände, die es auch geben soll.
Ein möglicher Weise a-typisches Verhalten in zu kleinen Aquarien hatte ich bereits angesprochen. Der Schlüssel hierfür würde mich sehr interessieren. Im Kern bleibt (salopp gesprochen) nur noch folgendes zu bemerken: Wenn das männliche Tier nicht immer "den Daumen drauf hat" , hat er das Nachsehen und muss in die zweite Reihe. Bestenfalls. 
Zitate aus einigen wissenschaftlichen Beschreibungen:
Many wrasses are organized into harem-based social systems and hermaphroditism is common (see Reproduction: Mating System)
Sex change in wrasse is generally female-to-male, but experimental conditions have allowed for male-to-female sex change. Placing two male Labroides dimidiatus wrasses in the same tank will result in the smaller of the two becoming female again. Additionally, while the individual to change sex is generally the largest female, evidence also exists of the largest female instead "choosing" to remain female in situations in which she can maximize her evolutionary fitness by refraining from changing sex.
Reproduction/Behavior
Blue Headed Wrasses are protogynous (female first) sequential hemaphrodites. This means that when the secondary male in a community dies, the largest female changes into a male.
Every afternoon, secondary males gather and wait for females to return from feeding (McIntyre). Terminal males are pair-spawning. They form “harems” and mate with only one female at a time. Secondary males experience huge breeding success. Estimates of breeding range from 25 times an afternoon (Deloach, 1995) to up to 40 times a day (Louch).
Primary males have little breeding success. Instead of mating one-on-one, they release sperm into the water. They must either covertly spawn with a female or travel in gangs, hoping to catch a female outside the sight of a secondary male. Often, they gather immediately outside the spawning sites of the secondary males, hoping to sneak access to females (Warner).
Habitat
Once hatched, juvenile fish have to find protection. Coral reefs provide the perfect habitat for protection from predators, food, and reproductive practices.
Breeding vs. Habitat
The specifics of breeding are different on large reefs and on small reefs. The plethora of wrasses found on large reefs enables primary males to experience high breeding success. The secondary males are often distracted and not able to constantly monitor females. In extremely large reefs, where it becomes very hard for males to defend females, the proportion of primary males in a population can reach 50% and theamount of secondary males can be as low as 19%.
On small and medium-sized reefs, there are fewer wrasses and primary males are very unlikely to have breeding success. Secondary males control all the favored breeding sites and monopolize mating (McIntyre). Consequently, the vast majority of wrasses are born female. However, Blue Headed Wrasses frequently experience socially controlled sex changes (Louch). When the secondary male dies or is removed, the largest wrasse (usually a female, but occasionally a primary male) begins changing color and within weeks, or even days, transforms completely into a secondary male (Deloach, 1995).
Gruß
Hajo