Dwarf Halfbeak - Dermogenys siamensis Fish Profile & Care Guide
Introduction
Dwarf Halfbeaks (Dermogenys siamensis) are widely sought after in the aquarium trade and can make an exceptional addition to a community aquarium. These fascinating oddball livebearers are particularly well-suited for nano or planted tanks.
Upon initial introduction to the aquarium, Dwarf Halfbeaks tend to be nervous and timid, often exhibiting erratic swimming patterns if startled, occasionally even colliding with the tank walls. However, as they acclimate to their surroundings, they become lively and relatively easy to care for.
The male-to-male combat behaviour of Dwarf Halfbeaks, which inspired the moniker "Wresting Halfbeak," is less intense compared to male Betta fish. While they are not a schooling species, a group comprising both male and female Dwarf Halfbeaks can coexist harmoniously in a community tank. Larger mixed groups with at least six males housed in spacious quarters with sufficient visual barriers are recommended to minimise territorial aggression among the males.
Dwarf Halfbeaks exhibit peaceful behaviour towards other species, making them suitable tankmates. It is advisable to select companions of similar size and temperament, such as other livebearers, Corydoras catfish, Kribensis Cichlids, Rainbowfish, and Barbs. However, caution should be exercised when pairing them with tiny fish or fry, as they may become prey, and it is best to avoid housing them with boisterous species that could intimidate the Halfbeaks.
To ensure optimal well-being, the aquarium should be positioned in a quiet area with a generous surface area. The skittish nature of these fish necessitates ample space to prevent damage to their delicate, elongated mouthparts when they exhibit sudden bursts of speed near the tank glass. Providing tall tangles of driftwood, dense planting, and ample surface cover from floating species will contribute to their sense of security. Efficient filtration is essential, although water movement should be gentle, and regular partial water changes are recommended to maintain minimal nitrate levels.
Dwarf Halfbeaks display sensitivity to abrupt changes in pH and water hardness. Nonetheless, they are generally adaptable and can thrive in various conditions, from soft and acidic freshwater to slightly brackish water. It is crucial to ensure the aquarium has a tightly-fitting lid, as these agile fish possess adept jumping capabilities.
These slender and elongated fish exhibit silvery bodies, with males showcasing a red dorsal fin, yellow tail, and anal fins. Females possess less intense colouring, typically featuring faint yellow hues in their fins, occasionally accompanied by a hint of red on the dorsal fin.
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Sexual Dimorphism
Distinguishing between male and female Dwarf Halfbeaks is relatively straightforward, as they exhibit distinct characteristics. Males can be identified by their smaller size compared to females. They possess a modified anal fin known as an andropodium, which plays a crucial role in their reproductive process. Additionally, mature males often display red or yellow patches on both the dorsal fin and beak, enhancing their visual appearance.
In contrast, females are larger in size and feature more subdued colouring compared to males. They also possess a small orange spot near the abdomen known as the gravid spot. This spot serves as an important indicator of the female's reproductive status. During pregnancy, the gravid spot enlarges, and males often select females based on the size of this spot, using it as a determining factor in their mate choice.
Quick Facts
| Scientific Name | Dermogenys siamensis |
|---|---|
| Year Described | 1934 |
| Other Names | Wrestling Halfbeak, Silver Halfbeak |
| Kingdom | Animalia |
| Classification | Actinopterygii |
| Order | Beloniformes |
| Family | Zenarchopteridae |
| Genus | Dermogenys |
| Origins | Thailand Vietnam |
| Approx Max Size | 7 cm |
| Temperament | Peaceful |
| Aquarium Level | Top |
| Difficulty | Beginner - Intermediate |
| Shoaling | No |
| Best kept as | Groups 6+ |
| Diet & Feeding | Omnivore |
| Reproduction | Oviparous |
| Average Lifespan | Up to 5 Years |
Water Parameters
| Water Type | Freshwater/Brackish |
|---|---|
| pH | 6.5 - 8.0 |
| GH | 10 - 20 |
| ℉ | 75 - 82 |
|---|---|
| ℃ | 24 - 28 |
Natural Habitat
The Dwarf Halfbeak, a species endemic to the Mekong and Chao Phraya River Basins between Thailand and Vietnam in western South East Asia, exhibits a restricted geographical range. Within this region, these Halfbeaks predominantly inhabit shallow, tranquil aquatic environments such as flooded fields, ponds, rivers, canals, ditches and lakes.
It is worth noting that some of these habitats may display stagnant characteristics, while others are characterised by abundant surface vegetation. During the rainy season, there have been occasional sightings of these fish in semi-brackish conditions near mangrove swamps.
Breeding
Breeding Dwarf Halfbeaks in a home aquarium setting has been achieved, although it is considered a moderately challenging endeavour. It is worth noting that after a female has successfully produced one or two broods, subsequent pairings may not always result in viable offspring. This issue is believed to be associated with a deficiency in certain vitamins, particularly vitamins A and D. To mitigate this risk, providing these fish with a high-quality and diverse diet is advisable.
Once fertilisation occurs, the female undergoes a 3 to 6 weeks gestation, influenced by temperature conditions. The typical brood size ranges between 10 and 30 fry. To enhance the survival rate of the fry and minimise predation risks, it is recommended to separate them from the adult population. Additionally, offering suitable nourishment such as baby brine shrimp and powdered first foods will facilitate their growth and development.
Diet & Feeding
In their natural habitat, Dwarf Halfbeaks primarily rely on feeding upon Drosophila fruit flies present on the water's surface. In a captive setting, providing these fish with a varied diet consisting of daphnia, brine shrimp, and bloodworms is recommended. Initially, these Halfbeaks may exhibit reluctance towards accepting dried foods. However, they can gradually acclimate to taking dried food into their diet with patience and consistent efforts.
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Published: 26 Jun 2023
Last Updated: 26 Jun 2023