Wrestling Halfbeak Breeding Guide

How to breed Dermogenys pusilla, a surface livebearer: sexing by andropodium, conditioning, a 3-6 week gestation, brood size and rearing live-born fry.

Overview

Dermogenys pusilla is a surface-dwelling livebearer of the family Zenarchopteridae from Southeast Asia. Unlike egg-laying killifish, females retain developing embryos internally and give birth to free-swimming fry. It is not as easy to breed as many common livebearers, although it is certainly possible.

Sexing

Males are the smaller sex and show a red patch on the dorsal fin that is absent in females. The defining male trait is the anal fin, which is modified into an andropodium, a reproductive organ used in mating. Reported sizes are males to about 5.5 cm and females to about 7 cm.

Conditioning

Condition adults on a varied diet that includes small live and frozen foods. Nutrition is critical for this species: many females produce stillborn young, a problem directly related to the nutrition of the fish, with some authors specifying a lack of vitamin D as a cause. Maintain breeders at 24-28 C, pH 6.5-8.0 and hardness around 10-20 dGH.

Breeding Setup

Provide a calm tank with floating plants at the surface, where these fish naturally orient, and a tight-fitting lid as they are strong jumpers. Low water flow suits the species. After internal fertilisation via the male's andropodium, gestation proceeds and fry are released directly into the water.

Spawning Behavior & Trigger

Males are territorial and the common name derives from their tendency to fight with each other, often locking jaws in the process; in aquariums these bouts usually end quite quickly. The gestation period is 3-6 weeks depending on temperature, after which the female delivers live young.

Egg & Fry Care

Broods are typically between 10 and 20 fry. Newborns are best removed, as the adults may predate on them. Fry readily accept powdered dry foods and brine shrimp nauplii from birth.

Common Challenges

The main difficulty is the production of stillborn young, linked to inadequate nutrition of the parents, so a high-quality varied diet during conditioning is essential. Jumping and the parents' tendency to eat fry are further practical concerns.