Dermogenys pusilla

Wrestling Halfbeak

Classification

Hemiramphidae

Distribution

Widespread in nature, it is known from India, Myanmar, Thailand, Laos, Cambodia, Vietnam, Phillipines, Malaysia and Indonesia.

Habitat

Tends to inhabit a variety of slow-flowing or still water biotopes, including rivers, canals, ditches, flooded fields, lakes and ponds. Some of these may be stagnant, and all typically contain lots of surface vegetation. It’s occasionally seen in semi-brackish conditions around mangrove swamps during the rainy season.

Maximum Standard Length

Male to 2.2″ (5.5cm), female to 2.8″ (7cm).

Aquarium SizeTop ↑

A small group could be kept in a 24″ x 15″ x 12″ (60cm x 37.5cm x 30cm) – 71 litre tank.

Maintenance

Surface area is more important than depth with this species, as it spends almost all of its time just under the water surface. It’s a particularly flighty species, particularly when first introduced to a new tank. The addition of dense planting around the edges of the tank will lessen the possibility of it damaging its delicate mouthparts by banging into the glass. It is also an excellent jumper, so a layer of floating vegetation is a good idea, as is a tightly-fitting cover. Decor below the surface is not essential and is a matter of personal preference. Salt can be added to a sg of around 1.005, but as long as the water is hard and fairly alkaline it should be ok in freshwater. Water changes should be small and frequent as is it sensitive not only to deteriorating water quality, but also to sudden swings in temperature or chemistry.

Water Conditions

Temperature: 75-82°F (24-28°C)

pH: 6.5-8.0

Hardness: 10-20°H

Diet

Feeds exclusively from the surface. Gut-loaded Drosophila fruit flies are an ideal food, but brine shrimp, bloodworm etc. are also taken. It sometimes refuses dry foods at first, but can usually be persuaded to accept them over time.

Behaviour and CompatibilityTop ↑

Can be kept with similarly-sized, peaceful species that enjoy the same water conditions. In a freshwater tank good choices include other livebearers, smaller rainbowfish and freshwater gobies. Under brackish conditions it can be kept with smaller glassfish (Parambassis sp.), bumblebee gobies and mollies. Don’t keep it with any much larger or more aggressive species, as it can become shy and will be easily outcompeted for food.

It can be kept in groups and will usually be less skittish when maintained in this way. Males will often spar with one another, but lasting physical damage is rarely done unless space is very restricted. It is best to keep either a single male specimen or several in order to disperse the aggression.

Sexual Dimorphism

The most obvious defining characteristic between the sexes is that the anal fin of males is modified to form an andropodium. This a genital–type organ, similar to the gonopodium of other livebearers. It is used in mating. Adult males also have a red patch on the dorsal fin that is absent in females, and are by far the smaller sex.

Reproduction

Not as easy to breed as many livebearers, although it is certainly possible. The difficulty does not lie with inducing the fish to breed, but that many females give birth to still-born fry. Apparently, this is directly related to the nutrition of the fish (some authors specify a lack of vitamin D as the cause), so ensure you offer them a high-quality diet.

It is best to keep a group of them in a species setup for breeding purposes. Furnish the tank as suggested above, with plenty of surface vegetation, condition the fish well, and mating should not present a problem. Gestation is heavily dependant on temperature, varying between 3-6 weeks. Assuming they are healthy, the fry are best removed, as the adults may predate on them. They are quite easy to feed and raise, accepting both powdered dry foods and brine shrimp nauplii from birth. Brood size is typically between 10-20.

NotesTop ↑

Halfbeaks derive their common name from the elongated lower jaw shared by all species. The ‘wrestling’ moniker given to this particular species is due to the tendency of males to fight with each other, often locking jaws in the process. It is used as a fighting fish in some of its native countries, with wagers being placed on the outcome of fights between males. The two fish are placed in a small container for fighting purposes, as they will spar incessantly in such confined conditions. In the aquarium, these bouts usually end quite quickly, the amount of space available meaning the weaker male can escape easily.

This species is probably the most commonly seen in the trade. It can be a little delicate when first imported, but once settled make an interesting surface dweller for the peaceful tank. Other, less commonly available members of the genus, such as D. siamensis and D. sumatrana are usually traded with the same common name when they are available.