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Halfbeaks & Needlefish
Halfbeaks and needlefish are closely related to one another, and comprise sister families within the Beloniformes. Juvenile needlefish pass through a ‘halfbeak stage’ of development where the lower jaw is longer than the upper jaw. For this reason, as well as various morphological similarities, it is believed that needlefish are descended from halfbeaks. The two groups occupy similar habitats in fresh water and sea, tending to live close to the surface in open water. Both have the same fusiform shape and are fast, efficient swimmers. The key difference between the two groups is that while halfbeaks are omnivores taking a mix of plankton, small invertebrates and algae, needlefish are predators, eating small fish as well as larger invertebrates such as shrimps and squid.
In aquaria, both need tank with plenty of open swimming space and a steady but not excessively turbulant current. Both halfbeaks and needlefish are nervous, flighty fish that will jump when alarmed. For this reason, the tank should be kept covered and aggressive tankmates avoided. Needlefish especially can harm themselves by swimming into the glass when frightened. Floating plants help them to feel more secure, and a few tall plants around the edge of the tank will reduce the chances of accidental collisions with the glass. Halfbeaks and needlefish have a reputation for being delicate, but this is mostly true when first imported, as they do not tolerate sudden changes in water chemistry particularly well. Once settled in though, halfbeaks at least are fairly robust. Needlefish remain quite demanding though, and should be kept only by experienced aquarists.
Halfbeaks are territorial, aggressive fish that constantly squabble, chasing one another around the tank and sometimes engaging in quite alarming fights. Males are the most aggressive, but females are only marginally less short tempered. Halfbeaks completely ignore other fish, and while they might eat small fish like livebearer fry, they are not particularly predatory and make good community tank residents. Needlefish are peaceful, schooling fish best kept in small groups. They are of course predatory and well able to eat small fish, but otherwise get along well with peaceful catfish and gobies of similar size.
Halfbeaks appreciate live foods including Daphnia, bloodworms, and brine shrimp, but in the wild all species are at least somewhat herbivorous. A diet containing vegetarian flake and frozen bloodworms will suit most species very well. Almost any small live foods are taken, including daphnia, brine shrimp, and mosquito larvae. Crustacean eggs are very popular, either frozen lobster eggs (sold for feeding marine invertebrates) or fresh shrimp eggs taken from coldwater shrimp bought at the fishmongers (in the UK at least, the shrimp have these eggs only in winter and spring). Halfbeaks also enjoy live insects, such as fruit flies and bluebottles.
Needlefish are entirely predatory, but contrary to popular belief, the Asian freshwater needlefish at least feeds primarily on crustaceans in the wild rather than fish. In captivity it will happily take river shrimps, mealworms, crickets, and other large insects. Needlefish can also be weaned on to frozen whitebait, lancefish, and so on, but feeding them some invertebrates each week is probably a good idea for their long term health. There is no particular need to feed them live fish.
Wrestling & silver halfbeaks
A variety of species are sold under this name, primarily Dermogenys pusilla, Dermogenys sumatrana, and Dermogenys siamensis. Telling them apart is not easy. These fish are relatively small, growing to between 4-7 cm (1.5-3 inches) in length.
Males Dermogenys are notoriously aggressive towards one another, and will fight. Except in a really big aquarium, or in ‘colony’ tanks containing dozens of specimens where aggression is spread out, it is best to keep just a single male alongside a group of females. Male fish are smaller, more colourful, and have a distinctively shaped anal fin with bent fin rays.
Dermogenys spp. are excellent halfbeaks for the beginner. They are hardy, tolerant of a wide range of water conditions, and easy to breed. The come from India and South East Asia and live in a variety of waters from soft and acidic through to slightly brackish (up to around SG 1.005 or so). Gestation takes about a month, and the female produces around ten to twenty offspring. She will miscarry if disturbed, and the prematurely born fry are difficult, probably impossible, to rear. On the other hand, properly delivered fry are hardy, grow relatively quickly, and will accept various small live foods as well as finely ground flake.
Celebes halfbeaks
Nomorhamphus liemi liemi is the species usually sold as the Celebes halfbeak, but a number of other species, such as Nomorhamphus ebrardtii, are sometimes included in batches of Celebes halfbeaks.
N. liemi liemi is quite a big fish, females getting to about 10 cm or so, though males are a bit smaller. They are brightly coloured, sporting red, blue, and black patches on their fins. Females have virtually no beak at all, while makes have a distinctively curled beak that forms a goatee-like structure. The other species typically lack the blue having differing amounts of red or yellow in their fins, if any at all, and unlike N. liemi liemi usually have straight beaks. Identifying these unknown halfbeaks is difficult.
These fish naturally inhabit freshwaters throughout South East Asia and will do best in slightly acidic, soft to moderately hard water. They can be adapted to very slightly brackish water as well (SG less than 1.003) but few species naturally inhabit such conditions and breeding them seems to be easier in soft water. The exception is Nomorhamphus ebrardtii, a species that does indeed live in brackish water in the wild and does not thrive when kept in soft and acidic water conditions. Nomorhamphus halfbeaks are fairly robust when settled in, and breed quite readily. Gestation is about a month or so, and a small brood (around a dozen) fry are produced. These are large and grow very quickly, and will feed readily on various live foods such as small daphnia.
River halfbeaks, Zenarchopterus spp.
Zenarchopterus spp. halfbeaks are true brackish water fish that will do well in either brackish or marine conditions. Some species seem healthy enough in freshwater, too, at least for short periods. Zenarchopterus buffonis is one species that is periodically traded. It is a big fish, around 20 cm (8 inches) when mature, and can easily be mistaken for a small needlefish. It is a schooling species and no aggression has been seen between specimens. Quite the reverse in fact: these fish are very nervous and cannot be mixed with anything aggressive or predatory. Best kept in their own aquarium. Nothing is known about their reproductive biology. Wild fish feed primarily on algae, plankton, and small invertebrates.
Bearded halfbeaks, Hemirhamphodon spp.
Various species of Hemirhamphodon are sometimes sold in aquarium shops, most frequently Hemirhamphodon pogonognathus. Though these are beautiful fish, they are not normally found in brackish water, requiring instead, clean, peat-filtered, very soft (near-zero hardness), and fairly acidic (pH 4.5-5.0) water to do well.
Needlefish
Xenentodon cancila or Asian needlefish are quite large predatory fish closely related to the halfbeaks and similar to them in basic shape. Maximum size in aquaria is around 30 cm (12 inches). They are sociable and need to be kept in groups, and consequently the aquarist will need to set aside a large aquarium for this species. Needlefish are very nervous. It is recommended that the tank be planted around the edges and back to allow the fish to recognise the boundaries of the aquarium and so avoid damaging itself when alarmed. These fish often jump, and can easily damage their jaws by flying into the hood or the sides of the tank. Floating plants and gradual rather than sudden changes in lighting will help. Needlefish prefer live foods including river shrimp, woodlice, earthworms, and insects such as mealworms and small crickets. They may also be weaned onto dead foods such as whitebait and silversides. Wild fish feed almost entirely on aquatic crustaceans; the idea that they feed on small fish is erroneous (though they certainly will eat small fish in the aquarium, given the chance).
Wild specimens are found primarily in freshwater and only rarely in brackish waters or the sea. Even so, a small amount of salt (around SG 1.001-1.002) is often said to improve its general health, and in captivity it can be expected to do well in low-salinity brackish water aquaria (to SG 1.005). Not an easy fish and best ignored by beginners, though experienced aquarists will doubtless find this species attractuve and rewarding.
Occasionally some other species are traded, such as various species of South American needlefish, Potamorrhaphis spp.; these have proved extremely delicate and difficult to keep alive. Most of these species need soft and acidic water but a few are brackish as well as freshwater animals. Either way, perfect water quality is required, and even then they do not seem to do well in captivity. Best avoided.