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Livebearers / Hemirhamphidae / Halfbeak

Halfbeak, Malayan Halfbeak, Wrestling Halfbeak
Dermogenys pusillus

Synonyms: Hemirhamphus pusillus
Physical description: An elongated fish with moderate lateral compression. The dorsal fin is set far back on the body, near the caudal fin. It possess a long immovable lower jaw. The upper jaw which can be moved up and down is smaller and shorter. The coloration varies, depending on where the specimen is found. Usually the upperparts are silvery-green to silvery-brown and the belly is silver to yellow. The fins for the most part are transparent although the dorsal and anal fins are both red at the base. The iris may be bright green in color. A red and green line extends across the lower jaw.
Size/Length: Females to 2.8" (7 cm), males to 2.2" (5.5 cm)
Similar species: D. pusillus sumatranus
Habitat: Shallow areas of fresh and brackish water rainforest rivers in coastal regions of Southeast Asia; Singapore, Thailand, Indonesia, Thailand, Malaysia, Borneo, Sumatra
S: top
Aquarium: A tank measuring 28" (71 cm) with a capacity of 20 gallons (76 L) is sufficient. The tank should have a cover of floating plants to provide protection for fry and a hiding place for the adults. Use a tight-fitting cover for these fish are excellent jumpers. Allow the growth of algae, for it serves to calm and comfort this nervous fish. The filter should create a slight current and a large open swimming area should be left open. Half-beaks prefer large, shallow tank having a lot of surface area.
Water chemistry: pH 7-8.5 (7.2), 6-18 dH (10), 70-86°F (21-30°C). A 1-1.5% addition of salt is recommended. This can be accomplished by adding 7.5-11 TSP. of salt to every 10 gallons (10-15 g/10 L)
Social behavior: A good community fish to combine with other live bearing species that can tolerate the addition of salt. Fish are best kept in a ratio of 2-3 females to one male, which helps eliminate male harassment of females. When first introduced, Halfbeaks are nervous fish that tend to be timid. However, once acclimate, Halfbeaks become lively fish. Males may often battle harmlessly with each other.
Suggested companions: Xiphophorus sp. (Platies and Swordtails), and Poecilia sp. (Guppies and Mollies), Celebes Rainbowfish
FOOD: Live; insects, mosquito larvae, small crustaceans, worms; flakes. Halfbeaks are surface-feeders.
Sexual differences: Male is slimmer with red patch on dorsal fin. Males possess an andropodium, an anal fin which appears folded.
Breeding techniques: Although the Halfbeak is a livebearer, it is not easy to breed. A water temperature between 75-82°F (24-28°C) is recommended. During spawning, male touches female's belly with his snout. Pregnancy lasts anywhere from 5 to 8 weeks. Often the fry are still-born, but this problem can be solved by feeding the parents vitamin food and a varied diet. From 10 to 70 young are born, each measuring about 1 cm (0.4"). The young or parents should be removed, for the parents will eat brood. Start feeding with Artemia nauplii and powdered dry foods.
Breeding potential: 7. Breeding is difficult for a livebearer.
Remarks: The Halfbeak is easily frightened, and may swim frantically around the tank and into tank glass, possibly causing injury, and often death. This nervousness will dissipate as later generations develop. Halfbeaks can be kept in water with a temperature slightly lower than 64°F (18°C), but it is not recommended because their activities slow.
Difficulty of care: 6. This fish is sensitive to unfavorable water conditions and requires frequent partial water changes. Live foods should be included in its diet.


By Rhett Butler   Mongabay.com