Wrestling Halfbeak

Dermogenys pusilla, the Wrestling Halfbeak, is a slender, surface-skimming livebearer from freshwater and brackish habitats across Southeast Asia. The common name refers to the spectacular jaw-wrestling contests that rival males engage in — locking their elongated lower jaws together and pushing against each other to establish dominance, rarely causing serious injury.

The asymmetric beak-like jaw — with the lower jaw much longer than the upper — is characteristic of the halfbeak family and is used to snatch insects and small invertebrates from the water surface. This species is an obligate surface feeder and will not accept food that sinks.

Wrestling Halfbeaks are viviparous livebearers that give birth to fully formed fry, though litters are small. They require a long aquarium with a large surface area and benefit from floating plant cover and a tight-fitting lid, as they are accomplished jumpers.

Water: 22–28 °C, pH 7.0–8.0, moderately hard; slight brackishness (1–2 g/L salt) often beneficial. Tank: 60 L minimum but long and wide; large surface area critical; tight lid essential — excellent jumpers. Feeding: Surface-feeding only; floating flake, live fruit flies, Daphnia, and mosquito larvae; will not take sinking food. Breeding: Small litters of 5–20 fry; gestation 4–8 weeks; remove fry immediately as adults may prey on them. Compatibility: Keep one male per tank or in a large tank; can be kept with mid- and bottom-dwelling peaceful fish of similar size.