FishFreshwaterIntermediate
©AI Generated·Proprietary
Wrestling Halfbeak
Dermogenys pusilla
An energetic surface-dwelling fish from Southeast Asia characterized by an elongated lower jaw. Males frequently engage in jaw-locking wrestling matches, requiring a covered tank to prevent jumping.
Water Temperature
24 - 28 °C
pH Value
7 - 8
Water type
Freshwater
Tank level
Bottom and middle
Adult size
7 cm
Minimum tank volume
>= 60 L
Minimum group
>= 3
GH
8 - 20 dGH
KH
6 - 15 dKH
TDS
200 - 500 ppm
Conductivity
313 - 781 uS/cm
Species description
Geographical Origin and Habitat: Native to Southeast Asia, inhabiting slow-moving rivers, canals, swamps, and flooded areas. It is highly adaptable to both freshwater and slightly brackish conditions.
Taxonomy and Morphology: Belongs to the Zenarchopteridae family. Grows up to 7 cm (2.8 inches). It is distinct for its elongated lower jaw, evolved for hunting small insects on the water surface.
Social Behavior: Strictly a surface dweller. Males are known for their intraspecific aggression, often "wrestling" by locking jaws (hence the common name). It is recommended to keep one male with several females in smaller setups, or multiple males only in very spacious tanks.
Coloration and Sexual Dimorphism: They have a slender, silvery body, often with delicate iridescent reflections. Males typically show red or yellow spots on the dorsal and anal fins and are smaller and slimmer than the more robust females.
Care, breeding and tankmates
Aquarium Setup: An aquarium with a large surface area is essential (minimum 20-gallon long). Abundant floating plants are crucial to provide hiding spots for fry and reduce stress for the adults. A tight-fitting lid is mandatory, as they are excellent jumpers.
Diet and Feeding: Primarily a surface insectivore. Thrives on live or frozen foods such as fruit flies (Drosophila), mosquito larvae, daphnia, and bloodworms. They will also readily accept high-quality floating flakes.
Water Quality: Prefers neutral to moderately alkaline water (pH 7.0-8.0) and medium hardness. Ideal temperature is between 75°F and 82°F (24°C-28°C). While they can live in pure freshwater, many keepers add a slight amount of marine salt, especially if the tap water is too soft.
Compatibility and Cohabitation: Very peaceful towards other species, practically ignoring bottom and mid-water dwellers. Excellent tankmates include peaceful Corydoras or small cyprinids that do not compete for the surface. Avoid boisterous fish that might startle them.
Aquarium Breeding: A livebearing species. Females can give birth to 10-20 fry at a time. Breeding can be tricky as females are prone to stillbirths if water conditions or diet are suboptimal. Fry require micro live foods and plenty of surface cover.
Risks and Diseases: Particularly susceptible to injuries to their delicate lower jaw, which can occur if they are startled and crash into the aquarium glass. They are also prone to shock if acclimated too quickly to different water parameters.
Geographic Origin and Distribution
Native to Southeast Asia, inhabiting slow-moving rivers, canals, swamps, and flooded areas. It is highly adaptable to both freshwater and slightly brackish conditions.
Origin
South and Southeast AsiaEast Asia
Fish profile
- Temperament
- Peaceful but territorial
- While peaceful towards other species, conspecific aggression among males is a defining behavioral trait. Males will often lock jaws and wrestle to establish dominance, which can occasionally lead to injuries if space is too constrained. Providing a heavily planted surface area and the correct sex ratio helps mitigate this aggression, resulting in a fascinating and dynamic display of natural behavior.
- Diet
- Insectivore
- Wrestling halfbeaks are strict surface feeders, naturally consuming insects that fall onto the water's surface in the wild. In captivity, they eagerly accept floating flakes and small floating pellets, but live or frozen foods are essential for their long-term health. Offering flightless fruit flies, mosquito larvae, Daphnia, and bloodworms will stimulate their predatory instincts and provide necessary protein.
- Life expectancy
- 2-5 years
- The lifespan of the wrestling halfbeak in captivity is generally between 2 and 5 years, although it is often shorter in the wild. To optimize their longevity, it is crucial to maintain stable water quality and avoid injuries to their delicate jaws. A nutritious, vitamin-rich diet promotes robust health and prevents premature aging. Controlling intraspecific stress among males contributes positively to their life expectancy.
- Adult size
- 7 cm
- The catalog's scalar value is 7 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 16.1 cm for this species, recorded as total length (TL). The taxonomic record consulted is Dermogenys pusilla (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Specific M:F ratio
- Males are known to be quite territorial and aggressive towards one another, frequently engaging in the "wrestling" matches that give the species its common name. To minimize conflict, it is strongly advised to maintain a ratio of at least two or three females for every male. If keeping multiple males, a larger tank with ample surface area and visual barriers like floating plants is necessary to allow subdominant males to retreat.
- Feeding frequency
- Twice daily
- Because they have small digestive tracts and are constantly active near the surface, feeding them small portions twice or three times daily is recommended. Care must be taken to only offer what they can consume in a few minutes, as any food that sinks past the upper layers will typically be ignored by them. Overfeeding can quickly foul the water, so monitoring their intake and cleaning up uneaten food is important.
- Bioload
- Low
- The bioload of the Wrestling halfbeak is considered moderate to low, making them suitable for appropriately sized aquariums with standard filtration. While they are relatively small, they require high water quality to remain healthy, so efficient biological filtration is a must. Regular water changes are critical to keep nitrate levels at a minimum and to prevent bacterial infections to which they are prone in poor conditions.
- Flow
- Moderate
- They appreciate a gentle to moderate water flow that mimics the slow-moving rivers and streams of their natural habitat in Southeast Asia. Too strong of a current will exhaust them, as they prefer to hover near the surface waiting for food. A gentle ripple on the water surface is beneficial for gas exchange and can help stimulate natural feeding responses without overpowering the fish.
- Jump risk
- Yes
- This species is notoriously prone to jumping, often leaping out of the water to catch insects or to escape perceived threats. A completely secure, tight-fitting lid with no gaps is absolutely mandatory when keeping Wrestling halfbeaks. Even small openings around filter pipes or heater cables must be covered to prevent tragic losses.
- Reproduction
- Livebearer
- Dermogenys pusilla is a livebearer, with females giving birth to relatively large, fully formed fry after a gestation period of several weeks. Pregnant females can be identified by a dark gravid spot and a swollen abdomen, though they may drop fewer fry than other common livebearers like guppies. To ensure fry survival, it is best to provide dense surface vegetation like floating plants for the young to hide in, or to isolate the female in a dedicated breeding or birthing tank.
- Compatibility & tankmates
- Community
- They are generally peaceful towards different species but should not be kept with large, aggressive, or fast-swimming fin-nippers that may harass them. Good tankmates include small corydoras, peaceful rasboras, and small bottom-dwelling loaches that won't compete for surface space. Due to their surface-dwelling nature, they largely ignore fish that inhabit the middle and lower regions of the aquarium.
- Tank level
- Middle/Bottom
- They are exclusive top-dwellers, spending the vast majority of their time swimming just below the water's surface. They are specially adapted to surface life, with their upturned mouths and flattened dorsal profiles allowing them to exploit this niche. They will rarely venture into the middle or lower levels of the tank, even to chase sinking food.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.4 ± 0.45 se
- Phylogenetic uniqueness (PD50)
- 0.5001
- Bayesian Length-Weight
- a = 0.00398, b = 2.89
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
