Wrestling Halfbeak (Dermogenys pusilla)

The Wrestling Halfbeak (Dermogenys pusilla), also known as the Malayan Halfbeak or Freshwater Halfbeak, is a slender, surface-dwelling livebearer from slow-moving streams, ditches, rice paddies, and coastal waters of Southeast Asia including Thailand, Malaysia, Singapore, and Indonesia. Its most distinctive feature is its elongated lower jaw — the characteristic that gives 'halfbeak' fish their name — which is used for surface-feeding on small insects and microorganisms.

Males are noted for their remarkable territorial behavior: when two males encounter each other, they lock lower jaws and engage in a pushing, wrestling contest that can last several minutes. This behavior inspired the common name and is harmless between well-matched individuals, though severe injury can occur in cramped spaces. Only one male per tank is recommended unless the aquarium is large with clear visual barriers.

Wrestling Halfbeaks are livebearers that give birth to free-swimming young after an approximate 30-day gestation. The fry are surface-oriented from birth and accept appropriately-sized surface foods immediately. Females can be aggressive toward each other in small spaces.

This species is peaceful toward other fish that don't compete for surface space and makes an interesting addition to planted community aquariums with appropriate tankmates.

Water Parameters: pH 6.5–8.0, temperature 22–28°C, GH 5–20. Adaptable to a range of conditions. Some specimens come from brackish environments and a small amount of aquarium salt (1 teaspoon per 10 liters) can benefit those individuals. Stable, clean water is important.

Tank Setup: Minimum 60 liters. Surface space and access are essential — avoid covering the surface fully. Floating plants (water lettuce, frogbit) provide cover and reduce surface disturbance. Dense fine-leafed plants along the perimeter. Gentle filtration with minimal surface current. Secure lid — they jump readily.

Feeding: Surface-feeders that prefer floating or surface foods: floating micro pellets, small dried insects (Drosophila), freeze-dried bloodworm, and live small fruit flies or mosquito larvae. They often refuse sinking foods. Feed at the surface twice daily.

Tankmates: Compatible with mid and bottom-dwelling peaceful species. Avoid other surface dwellers that compete for feeding zones. Keep ONE male per tank unless the aquarium is large. Females can be kept in small groups. Avoid aggressive or fast-moving species that stress them.

Breeding: Livebearers producing 5–20 fry per brood after 4–6 week gestation. Fry are surface-oriented and accept small floating foods from birth. Provide floating plant cover to protect fry from adults.