Moon Wrasse Breeding Guide (Thalassoma lunare)
Thalassoma lunare is a protogynous, pelagic-spawning reef wrasse that changes sex from female to male in about ten days; it is not home-bred, and this guide documents its real reproductive biology.
Overview
The moon wrasse (Thalassoma lunare) is a Labridae wrasse native to the Indian Ocean and western Pacific, where it inhabits coral reefs at depths of 1 to 20 m. It can reach 45 cm in total length. Adults have a green body with marked scales and a head ranging from blue to magenta, while the dark juvenile tail blotch develops into the characteristic yellow crescent on maturation.
Sexing
The moon wrasse is a protogynous hermaphrodite that begins life as a female and can later transform into a male. Wikipedia reports that this sex change takes only about ten days for this species. Because individuals shift sex with social context and colour intensifies in dominant males, fixed visual sexing of a given fish is unreliable; the most vivid all-blue colour appears in the breeding-season dominant male.
Spawning Behavior & Trigger
During the breeding season the dominant male becomes completely blue, gathers females, and spawning occurs before high tide. As an oviparous reef wrasse it is a pelagic broadcast spawner, releasing gametes into the water column so fertilised eggs drift away as plankton. The tidal timing is the documented natural trigger; no captive trigger has been established.
Egg & Fry Care
Fertilised eggs are pelagic and develop into planktonic larvae carried in open water. This dispersal-larvae phase is the central obstacle to captive rearing, as the larvae are minute and demand live planktonic food unavailable at scale in a home tank. No home-aquarium fry-rearing data exist for the species.
Common Challenges
The moon wrasse is active, territorial and carnivorous, feeding on fish eggs and small invertebrates, so it is not reef-safe and would consume tankmate spawn. Its large adult size (up to 45 cm) demands a very large system, and the unreared pelagic larval stage closes off home breeding. It remains a wild-caught fish in the trade.