Common name: Wrestling halfbeak

Scientific name: Dermogenys spp.

Family: Hemirhamphidae

Origin: South and South East Asia; most imported fish are from Thailand and Indonesia

Maximum size: Typically around 5 cm, rarely up to 7 cm

Minimum Tank Size: Length at least 60 cm, depth relatively unimportant

Care: Wrestling halfbeaks of the genus Dermogenys inhabit a variety of waters from soft and acidic through to slightly brackish. While Dermogenys pusilla apparently does best in slightly brackish water as far as captive care goes, a variety of species are sold under the wrestling halfbeak name, others prefer somewhat soft, acidic to neutral water conditions, as with Dermogenys montanus and Dermogenys sumatrana. Importers and retailers make no attempt to separate these species before slling them, and they are in fact very difficult to tell apart. The safest approach is therefore to keep these fish in neutral, slightly soft to moderately hard water and only add salt if it is obvious that the fish are unhealthy. As with other halfbeaks, they do not tolerate large changes in water chemistry, so small but frequent water changes are best (I do around 5% once or twice a week). These fish also appreciate plenty of floating plants amongst which to hide, particularly if they are kept in a community tank with other, more boisterous, species.

Social Behaviour: Females are fairly tolerant of one another and will sometimes swim in pairs or small groups, but males are very aggressive towards one another. Their fights can lead to injuries, so it is best to keep only a single male per tank except in large tanks with plenty of places for weaker males to hide. Be prepared to remove these fish if they a being constantly harassed. These halfbeaks are otherwise peaceful, and should not be combined with aggressive or substantially larger fish.

Feeding: Readily takes live, frozen, and flake foods. Small insects and insect larvae are the best foods, and excellent for conditioning the females and keeping them healthy during pregnancy.

Sexing: The anal fins of the males are modified and appear "folded", producing a structure analogous to the gonopodium of poecilid livebearers like guppies and mollies. Males of some varieties of wrestling halfbeak have red or red-and-yellow dorsal, anal, and caudal fins, but not all.

Breeding: Similar to the red fin halfbeak. Pregnancy length very variable, from three to eight weeks depending on the species of halfbeak. Broods typically around a dozen fry, which are able to eat small live foods and frozen lobster eggs immediately after birth.

Comments: Wrestling halfbeaks are much smaller and more slender than Celebes and red fin halfbeaks of the genus Nomorhamphus. They also tend to stay close to the surface of the aquarium whereas Celebes halfbeaks spend a lot of time swimming in the middle of the tank. Small Nomorhamphus spp. could be mistaken for Dermogenys spp.; the best way to distinguish them is by looking at them from above. Whereas the beaks of Dermogenys are bordered by transparent 'flanges' creating a scoop-like structure, those of Nomorhamphus lack these flanges and appear more needle-like.

© Neale Monks

This post has been edited by nmonks: Mar 8 2008, 12:54 PM