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I've never understood why so many aquarists dismiss livebearers as being fit only for beginners. Part of the problem might be that many aquarists are unaware of the sheer variety of livebearers. Among the cartilaginous fishes, giving birth to live young is actually more common than laying eggs: great white sharks, hammerheads, and sand tigers are livebearers, just like guppies! Other unfamiliar livebearers are the two living species of coelacanth and a group of marine fish very closely related to the cichlids called the surfperches.
Fishkeepers recognise five families of livebearing fish as being suitable for aquarium life, of which one family, the Poeciliidae, predominates. This family includes the guppies, mollies, platies, and swordtails, as well as a large number of other, less familiar, species well worth hunting down. Within the toothcarp order alongside the Poeciliidae are the families Goodeidae and Anablepidae, known as the splitfins and the four-eyed fishes respectively. The freshwater halfbeaks of Asia are in some ways analogues of the American Poeciliid and Goodeid livebearers, being not only livebearers but sharing many other physical characteristics, such as strong sexual dimorphism and an upturned mouth ideally suited for feeding on mosquito larvae and other insects. The fifth family of livebearing aquarium fish is the Potamotrygonidae, a small family of stingrays confined to tropical South America. Being large, demanding animals suitable only for the most experienced and dedicated aquarists, they fall outside the scope of this article, and nothing more will be said about them. Instead, the focus is on species that are easily obtained, not too difficult to keep, and small enough to work well in the average home aquarium.
Starting our review of the livebearers alphabetically, the four-eyed fishes of the genus Anableps certainly qualify as being decidedly un-boring fish. In fact, it would be hard to find more interesting aquarium fish. Their most celebrated features are their eyes, which are each divided into two lobes, one for seeing above the waterline, and the other below. This specialisation presumably allows them to hunt for food and avoid predators at the same time, and these fish are certainly nervous, jumpy fish that take a long time to settle into aquarium life.
The other famous oddity is that these fish aren't just male or female; they're 'right-handed' or 'left-handed' as well. Females have a covering, called a foricula, over the genital opening that is hinged on either the left or the right hand side of the opening. If the foricula is hinged on the right, the genital opening is only clear on the left, and vice versa. Males have a gonopodium, a modified anal fin, that delivers sperm to the female, and again, it either bends to the left or to the right. A male with a gonopodium that bends to the right can only mate with a female that has its genital opening open on the left, and left-handed males can only mate with females that are open to the right.
In terms of aquarium care, four-eyed fish are quite demanding. The first issue is size: these are big fish, getting to around 25-30 cm in length. Females are usually a bit bigger than the males, but if you want to breed these fish, you're going to need to keep at least half a dozen specimens just to make sure you get compatible males and females. Consequently, a big aquarium with plenty of filtration is essential. Complicating things somewhat is the need these fish have for 'resting' places. In the wild, these fish beach themselves on sandbanks, but in aquaria, large, smooth stones or flat pieces of slate will work perfectly well. Arrange these so that they form a ledge a just far enough under the waterline that the fish can rest with just their eyes protruding. Finally, these are brackish water fish, and do not do well when kept in completely fresh water. The exact saltiness of the water isn't critical, but a specific gravity between 1.005 and 1.010 will do nicely.
Despite being livebearers, breeding these fish isn't especially easy. As with some of the other oddball livebearers, the tricky bit is making sure the female doesn't miscarry. Providing optimal water conditions and a stress-free environment is half of the battle here, but keeping her in good conditions by providing plenty of live and frozen foods is just as important. The baby fish are born after a gestation period of about three months, and they are about 5 cm in length, easily big enough to small brine shrimp, daphnia, bloodworms, and other small foods. The parents aren't especially cannibalistic, but removing them to a separate maturing tank is a good idea, if only so that you can ensure that the baby fish get plenty of food.
Excerpted From: So you think livebearers are boring? There's more to livebearers than guppies. Neale Monks looks at some of the interesting and unusual livebearers available to aquarists by Neale Monks
Although the splitfins have been overshadowed by the poeciliids, they remain good aquarium fish and in recent years a fair number have become quite commonly traded. For the aquarist wanting to try their hand at one of 'rare livebearers', Goodeids are an excellent choice. Most are hardy, easy to keep, and do very well in the hard, alkaline water typical of much of England. If they have one failing it is that many are a pushy, even nippy, fish that don't always play nicely with their tankmates. But kept with their own kind, or robust species such as catfish, and these are colourful and fascinating animals.
What sets the Goodeids apart from the poeciliids is that they are viviparous fish rather than ovoviviparous ones. In other words, they become pregnant in the same way mammals do, with the embryo being connected to the mother via a placenta-like structure called the trophotaenia. This allows these fish to produce larger, more fully developed offspring than the poeciliids. Indeed, immediately after birth, the sharp-eyed aquarist will spot the remains of an umbilical cord trailing off the belly of the newborn fish. On the other hand, since the individual fry are quite big, typically around 2 cm long at birth, the broods are rather small, often in the high teens or low twenties.
Two species of Goodeid are widely sold, Ameca splendens and Xenotoca eiseni. Both are hardy, reliable fish for anyone wanting to keep oddball livebearers. They aren't perfect community fish though, and this is perhaps the only thing that limits their popularity, as both are very pretty and lively little fish. Compared with the common poeciliids like guppies, both these species can be aggressive towards one another and any tankmates kept with them. Of the two, Ameca splendens is perhaps the most easily kept with tankmates. While it is aggressive and will bully things like tetras, rainbowfish, and Corydoras catfish, more robust tankmates, such as armoured catfish, sturdy barbs, and semi-aggressive (but non-predatory) cichlids generally work well. Xenotoca eiseni is similar in temperament but is also a fin-nipper, so tankmates that move slowly or have long fins should be avoided.
All Goodeids need a lot of algae in their diet, and unless fed copious quantities of greenstuffs, they tend to lose their bright colours. This is one reason they tend not to look especially exciting when held in retailers' tanks, where they receive only standard-issue flake food. On the upside, being largely vegetarian, most Goodeids show little tendency towards eating their offspring, and in a well-planted aquarium, the fry can be raised with their parents.
While at least half a dozen species of halfbeak are commonly traded, retailers simply divide them up into Celebes halfbeaks for the various species of Nomorhamphus, and silver (or wrestling) halfbeaks, which cover species of Dermogenys. Celebes halfbeaks are larger and more colourful, but they have a reputation for being rather delicate and short-lived fish. This is almost certainly because retailers do not correctly identify the different species sold, and not all species have the same water chemistry requirements. The most commonly traded species is Nomorhamphus liemi, the true Celebes halfbeak, which needs slightly soft and acid water to do well. By contrast, the red-fin halfbeak, Nomorhamphus ebrardtii, the next most commonly sold species, must have hard and alkaline water to do well. Distinguishing these two species is fairly easy: Nomorhamphus ebrardtii have straight beaks and red or orange fins, whereas Nomorhamphus liemi have curly beaks and red, black, and blue fins. A few other species are sometimes sold as Celebes halfbeaks, and generally these resemble Nomorhamphus liemi in terms of water chemistry requirements.
Silver halfbeaks, on the other hand, are very hardy, and though they lack the bright colours of the Celebes halfbeaks, they have more 'halfbeaky' shape, with a nice long snout and a very streamlined shape. There are probably three different species of Dermogenys sold under the silver halfbeak name, and all will tolerate a broad range of water chemistry values. They will even do well in slightly brackish water.
In terms of care, these are fairly straightforward fish. Flake foods are readily taken, though for breeding purposes, conditioning the fish with frozen or live foods is essential. Bloodworms, daphnia, fruit flies, and other small invertebrates are particularly favoured. Silver halfbeaks feed almost exclusively from the surface, while Celebes halfbeaks are much more midwater fish, and will even take food from the substrate. All halfbeaks are jumpy, easily startled fish, and ensuring the tank is covered at all times is essential. Floating plants will help to settle these fish into the aquarium, as well as providing the fry with somewhere to hide. One peculiar characteristic of the halfbeaks generally is the high level of aggression they display to one another. Females are only marginally less aggressive than males, and both sexes will engage in short chases and fights. Although males do not fight to the death, the cumulative stress of being bullied by a dominant male can lead to the premature death of other males in the tank. For this reason, halfbeaks should be kept in either a big group (over a dozen) or in a smaller group with only a single male.
Halfbeaks are fairly easy to breed; about the only problem is keeping the mother happy and healthy through the gestation period. Unlike most other livebearers, miscarriages are common with halfbeaks, perhaps due to their nervous temperament. Once born though, the baby halfbeaks are tough and easy to raise, and will immediately accept newly hatched brine shrimps, small daphnia, frozen lobster eggs, and finely ground flake food.
The poeciliids are the standard-issue livebearers in many peoples' eyes, but there is a very surprising degree of variation among them. In general though, these are excellent aquarium fish. Most species are small, more or less peaceful, and often brightly coloured. While the wild-type fishes might lack the sheer gaudiness of the artificial varieties of guppy or molly, they are still very nice fish. One quick side note about wild-type poeciliids worth making is that most like very warm water, at least 25Ë°C, and often as high as 30Ë°C. This is important to consider when breeding these fish, as lower temperatures reduce your chances of success.
Probably the only place to start looking at oddball poeciliids is the pike livebearer, Belonesox belizanus. This is a big, predatory fish that closely resembles our own native pike in shape, colouration, and habits. Its preferred diet is smaller fish, particularly other livebearers, and it will also eat smaller individuals of its own species. This causes a particular problem for anyone interested in breeding this fish: it is not unknown for females to eat the rather smaller males. Besides fish, younger specimens will readily take large insects and insect larvae, and some aquarists have managed to keep such fish on an insect-only diet for their entire lives. Wild-caught adults are generally much more difficult to wean onto other foods, though it can be done. Obviously, being fish-eaters, these animals will devour their offspring without a second thought; so providing plenty of floating plants for any fry to hide in is essential.
At the other extreme, the porthole livebearer, Poeciliopsis gracilis, is a small, peaceful Poeciliid that has proven to be durable and easy to keep. It is not fussy about water chemistry, and being tolerant of slightly soft and acidic water, is one of the few livebearers well suited to tanks otherwise designed for things like tetras and rasboras. It is delightfully active, and this more than makes up for its slightly plain colouration, essentially greenish-silver with a series of round back spots on the flanks. Indeed, these fish make excellent dither fish for things like gouramis and dwarf cichlids.
Another lovely little livebearer is the dwarf killifish, Heterandria formosa. This is a tiny fish: males are barely 2 cm long and very slender, though females are a bit bigger and more robust. A peculiarity of this species is that it doesn't produce discrete batches of fry like most other poeciliids, but instead a few fry are dropped every day across a period of several weeks. These fish are pretty benign towards newborn fry though, and so in a well-planted aquarium, there shouldn't be any problems finding the fry and removing them to another tank. From the dwarf killifish through to the fearsome pike livebearer, the poeciliids really do make it clear that livebearers are far from boring!
Common name: Four-eyed fish
Origin: Atlantic and Pacific coastlines of northern South America
Maximum Size: 30 cm
Water requirements: Brackish water
Food: Most floating foods, especially insects and insect larvae
Social behaviour: Schooling fish, very nervous and prone to jumping; do not keep in an uncovered aquarium
Breeding: Gestation period around 3 months; juveniles require small live foods such as brine shrimps, mosquito larvae, and daphnia. May take finely ground flake as well
Common name: Butterfly Goodeid
Maximum Size: Females up to 10 cm, males smaller
Water requirements: Hard and alkaline freshwater
Food: Flake, bloodworms, algae, soft-leaved plants
Social behaviour: Fairly peaceful towards one another, but often aggressive towards other fishes; best kept with larger, robust species such as catfish and non-predatory cichlids
Breeding: Gestation period around 2 months; juveniles easily raised on finely ground flake, algae, and small live foods such as daphnia
Common name: Red-tailed Goodeid
Maximum Size: Females up to 8 cm, males smaller
Water requirements: Hard and alkaline freshwater
Food: Similar to Ameca splendens
Social behaviour: Similar to Ameca splendens, but also a confirmed fin-nipper
Breeding: Similar to Ameca splendens
Common name: Silver or wrestling halfbeak
Origin: South East Asia
Maximum Size: Females up to 7 cm, males smaller
Water requirements: Anything from soft and slightly acidic through to low-end brackish
Food: Flake and small insects
Social behaviour: Aggressive towards one another, but otherwise peaceful
Breeding: Gestation period variable but typically around six weeks; fry can be raised on finely ground flake and small live foods
Common name: Celebes halfbeaks
Origin: Sulawesi (Indonesia)
Maximum Size: Females up to 11 cm, males much smaller
Water requirements: Most species prefer soft and acidic to neutral freshwater, but not all
Food: Similar to Dermogenys spp.
Social behaviour: Similar to Dermogenys spp.
Breeding: Similar to Dermogenys spp.
Common name: Pike livebearer
Origin: Central America
Maximum Size: Females typically around 15 cm, males smaller
Water requirements: Warm (up to 30Ë°C), hard, alkaline freshwater or slightly brackish water preferred
Food: Primarily smaller fish, but also large insects, earthworms, frozen silversides, etc.
Social behaviour: Peaceful though predatory
Breeding: Gestation period is at least one month; the juveniles will eat any small animal they can catch: brine shrimp, bloodworms, daphnia -- and one another!
Common name: Porthole livebearer
Origin: Central America
Maximum Size: 5 cm
Water requirements: A freshwater species, doing well in either slightly soft and acidic through or slightly hard and alkaline
Food: Flake, insect larvae, and algae
Social behaviour: Lively and peaceful
Breeding: Gestation period is around a month, and the fry can be raised on finely ground flake, algae, and small animals such as daphnia
Common name: Dwarf killifish
Origin: North America
Maximum Size: Males 2 cm, females 3.5 cm
Water requirements: Hard, alkaline freshwater preferred
Food: Flake, insect larvae, and algae
Social behaviour: Lively and peaceful
Breeding: Small numbers of fry are dropped more or less continuously