Betta Breed · Thailand (domestic line)
Halfmoon
Caudal fin spreads 180 degrees — the benchmark modern show tail type.
By the WARN Research & Conservation TeamChecked against IUCN Red List & CITES sourcesLast updated
In brief
The Halfmoon betta spreads its caudal fin 180 degrees when flared — the benchmark modern show tail type line-bred in Thailand and internationally. Its defining trait is spectacular finnage demanding heated filtered tanks of at least 19 litres, never unheated vases or bowls.
Halfmoon: At a Glance
| Origin | Thailand (domestic line) |
|---|---|
| Size | Small (5–7 cm body) |
| Typical size | 5–7 cm (2–2.8 in) body excluding tail; long fins add display size |
| Lifespan | 3–5 years (with excellent care) |
| Fins & colour | Long flowing fins across caudal, dorsal and anal with full semicircle spread when flared. Colours span solid, bi-colour, marble and dragon combinations. Delicate fin edges tear on sharp plants and strong filter flow. |
| Temperament | Territorial, solitary, showy |
| Best suited to | Solitary male tanks or carefully planned divided aquaria — halfmoons need 25–28 °C heated water, gentle filtration and soft live or silk plants. |
History & Origins
Halfmoon bettas were line-bred from delta tail stocks in Thailand during late twentieth century, dominating contemporary IBC show standards alongside plakat and crowntail types. British pet trade sells halfmoons widely — buyers must provide filtered heated tanks, not desktop bowls marketed for bettas.
Halfmoon Fun Facts
- Halfmoon spread requires 180-degree caudal arc when fully flared.
- All bettas are Betta splendens morphs — not separate wild species.
- Male halfmoons build bubble nests even without females present.
- Fin weight slows swimming versus plakats — avoid strong filter outflow.
Halfmoon Common Health Issues
Conditions seen more often in this breed, and how owners and vets help manage them. This is general guidance, not veterinary advice — always speak to your vet.
Fin rot
Bacterial fin edge recession from ammonia burns or injury.
Care: Improve water quality; vet-approved antibiotics if recession continues.
Poor water quality sensitivity
Long fins trap bacteria in unfiltered bowls.
Care: Filter, heater and weekly partial changes.
Labyrinth organ stress from cold water
Cold reduces immunity despite air-breathing ability.
Care: Thermostatic heater set 25–28 °C.
Bettas need heated, filtered tanks
Siamese fighting fish are sold in cups worldwide — yet they thrive in heated, filtered five-gallon-plus tanks with enrichment. Better care starts with honest information.
