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Wrestling Halfbeak
Dermogenys pusilla
Animalia›Chordata›Actinopterygii›Beloniformes›Zenarchopteridae
📍 Southeast Asia
A unique surface-dwelling livebearer with an extended lower jaw resembling a tiny swordfish. Males spar by locking jaws in non-harmful wrestling matches. An unusual addition to peaceful community tanks with a tight-fitting lid.
Care Guide
Diet
Wrestling Halfbeaks are strict carnivores requiring live or frozen foods such as small insects, mosquito larvae, brine shrimp, and small crustaceans. Feed small portions once daily, as they prefer to hunt at the water surface. They rarely accept dry foods and may starve if only pellets are offered.
Behavior
These surface-dwelling fish are semi-aggressive, particularly males which engage in jaw-locking contests to establish dominance. They are active hunters that spend most time at the water's surface, making them fascinating to observe. They can be skittish around sudden movements and prefer tanks with minimal disturbance.
Breeding
Breeding in captivity is possible but challenging and rarely occurs in home aquariums. Males are highly aggressive toward each other during breeding season, requiring separation into individual tanks. Females are livebearers producing small numbers of fry; successful breeding requires pristine water conditions and abundant live food for fry.
Tank Mates
Similar size and peaceful temperament; occupy different water zones reducing competition
Small, non-aggressive schooling fish that won't compete for surface feeding areas
Bottom-dweller that doesn't compete for surface food; helps maintain tank cleanliness
Peaceful invertebrate that occupies different ecological niche; won't be harmed by halfbeaks
May compete for surface space; monitor for aggression, particularly during breeding
Common Diseases
Ich (White Spot Disease)
White spots on body and fins, flashing against surfaces, labored breathing
Raise temperature gradually to 28-30°C, perform daily 25% water changes, use aquarium salt (1 tsp per 5 gallons) or ich medication for 7-10 days
Fin Rot
Frayed or deteriorating fins, discoloration at fin edges, lethargy
Improve water quality with frequent changes, remove decaying food, treat with antibacterial medication if severe
Mouth Fungus
White cottony growth around mouth and jaw area, difficulty feeding, jaw deformity
Isolate affected fish, treat with antifungal medication, maintain excellent water quality and temperature stability
Starvation
Extreme thinness, lethargy, loss of color, refusal to eat
Provide varied live foods (mosquito larvae, daphnia, small insects); ensure food reaches surface where they feed; may require hand-feeding
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Quick Facts
- diet
- Carnivore – floating foods, fruit flies, freeze-dried bloodworms
- lifespan
- 3–5 years
- max size
- 7 cm (2.8 in)
- tank size
- 15 gallons minimum
- temperament
- Peaceful, males spar harmlessly
Water it likes
- ph
- 6.5–8.0
- ammonia
- 0 ppm
- nitrate
- <20 ppm
- hardness
- 8–20 dGH
- temperature
- 75–82°F (24–28°C)