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Dermogenys pusilla
This week’s Fish of the Week is an oddball species that can make a fantastic addition to the community aquarium. The wrestling halfbeak (Dermogenys pusilla) is widespread throughout South East Asia. They are found in both freshwater and brackish environments. It is a livebearing (ovoviviparous) species similar to guppies and swordtails and exhibit sexual dimorphism. The males are smaller (up to 5cm), more colourful and have a modified anal fin (andropodium) to hold on to the females during mating. Fish in the family Poeciliidae (guppies, swordtails etc) have a similarly modified anal fin called the gonopodium, which is used to internally fertilise the females. The female Wrestling Halfbeak grows much larger (up to 7cm) and are more bland in colour. They also possess a small orange spot near the abdomen called the gravid spot. It enlarges during pregnancy and males often choose females by the size of this gravid spot.
Their common name comes from the large elongated lower jaw of all species of halfbeaks. The fighting style between males gave rise to the name 'Wresting Halfbeak'. These fights tend to be less intense than Betta males and a group of males and female halfbeaks can be kept together in a community tank.
Halfbeaks spend their lives near the top of the tank, and are well adapted to life at the surface. Their elongated bottom jaw helps catching small prey items that land on the surface, complete with sharp teeth. The small size of the wrestling halfbeak means they will not predate their tankmates, except for nano fish and young fish. They may only take frozen foods when first introduced to the aquarium, but given time they should take a quality floating food.
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Tagged in: Fish of the Week Archive - Freshwater, Indoor