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  • Species: Costello Tetra

  • Species: Crenuchus spilurus

  • Species: Flametail Tetra

  • Species: Hyphessobrycon loweae

  • Species: Iguanodectes spilurus

  • Species: Nematobrycon lacortei

  • Species: Markiana nigripinnis

  • Species: Paracheirodon simulans

  • Species: Pterobrycon myrnae

Rare and unusual tetras from South America

The range of tetras exported from South America has been steadily increasing over the years. In this article we’ll be looking at some of the less familiar tetras currently imported. While most are eminently suitable for the community tank, some have particular needs that make them challenging in one way or another. These tetras also tend to be wild-caught rather than farmed. On the one hand, this means that they are less likely to suffer from inbreeding or disease, as is all too often the case with intensively farmed Neon Tetras and the like. But being wild-caught fish, these tetras are often fussier about their food and less adaptable in terms of water chemistry, so appropriate care will need to be taken when settling them in.

Basic care

Tetras are mostly schooling fish, and the more you keep, they happier (and healthier) they will be. Schooling species should be kept in groups of no fewer than six specimens, and ideally keep them in groups of ten or more for best effect. Big groups are more likely to school together properly, and the interactions between males and females ensure that their optimal colours are displayed. In groups that are too small the fish tend to be nervous, exhibit weaker colours, and may be prone to aberrant behaviours such as aggression and fin-nipping.

Most South American tetras come from soft, slightly acidic waters. In general aim for water with a pH between 6 and 7.5, and hardness levels between 5 and 15 degrees dH. Water temperature is generally not a critical issue, but some tetras do prefer slightly cooler or warmer conditions than otherwise, so this should be reviewed before adding them to the community tank.

Almost all tetras are insectivorous, feeding on insect larvae and aerial insects that fall onto the surface of the water. In captivity they are typically adaptable feeders that enjoy live and wet-frozen foods but readily take flake and micro-pellet foods without complaint. A balanced diet is important for long term health, and occasional offerings of things like live brine shrimp and daphnia will ensure good colouration and minimise the risk of health problems such as constipation that can be caused by a diet based solely on dried foods.

Kept properly tetras are typically hardy fish that can be fully expected to live a normal lifespan of around five years. Whitespot is probably the most common health problem, and usually only an issue with newly purchased specimens. If you can, quarantine new stock for six weeks before adding them to your display aquarium.

Costello Tetra, Hemigrammus hyanuary

There are at least 50 species of Hemigrammus known, all of which are small, schooling fish. Many of them turn up as aquarium fish from time to time, including such favourites as the Glowlight Tetra (Hemigrammus erythrozonus) and the Rummynose Tetra (Hemigrammus bleheri). The Costello Tetra is a small (to 4 cm) less often seen member of the genus, with a slender, silvery body marked with two coppery patches, one above the eye and the other on the caudal peduncle. Sexual dimorphism is slight, with the males being a bit more slender than the females and having a hook-like structure on the anal fin. Basic care is much like other Hemigrammus, the species needing to be kept in a group of at least six specimens and kept with small, peaceful tankmates. Like many tetras its colouration is dependent on its environment, and to get the best from this species it should be kept in a dark, shady tank with plenty of plants. The Costello Tetra is not fussy about environmental parameters, but does best at a middling to somewhat warm temperature (24 to 28 C) in water that is not too hard or basic (pH 6-7, 5-10 degrees dH).

Flametail Tetra, Aphyocharax erythrurus

Aphyocharax species such as the Bloodfin Tetra (Aphyocharax anisitsi) have a well-earned reputation for being easy to keep and well suited to community tanks. The Flametail Tetra, Aphyocharax erythrurus is no exception, and though it isn’t as widely traded as the Bloodfin, it is certainly worth looking out for. Getting to a length of a little over 6 cm, these fish are slender, silvery animals with a brilliant patch of scarlet across the caudal peduncle and the central portion of the tail fin. They are otherwise unmarked except for a slight blackening around the snout. Males and females appear to be identical. They are not fussy about water chemistry, and do well in both soft and moderately hard water. Although they enjoy swimming out in the open, they do appreciate the shade that a planted aquarium provides, and should also be kept away from aggressive tankmates likely to bully them. On the other hand, their liveliness makes them ideal dither fish for things like Apistogramma and gouramis.

Green Neon Tetra, Paracheirodon simulans

The Green Neon is closely related to both the Neon Tetra (Paracheirodon innesi) and the Cardinal Tetra (Paracheirodon axelrodi). In terms of appearance it resembles the Neon most closely, with a greenish-blue band running from snout to tail and a partial red band running beneath the greenish-blue band between the pelvic fins and the caudal peduncle. Like the Neon, it is also quite a small tetra, with a maximum length of about 3 cm. However, it more closely resembles the Cardinal Tetra in requirements, needing fairly warm (25 to 28 degree C) water that is both soft and acidic (pH 6-7, 5-10 degrees dH). In general terms this species has proven to be a bit delicate, and while very attractive in a mature, well-planted aquarium it is not a good choice for the average community tank. It is also rather a shy species, so needs to be kept in a large group to feel settled. Otherwise, basic care is much like that of Neons and Cardinals.

Kitty Tetra, Hyphessobrycon loweae

There are at least 120 species of Hyphessobrycon, including numerous species that regularly turn up in aquarium stores, such as the Belgian Flag Tetra (Hyphessobrycon heterorhabdus), the Bleeding Heart Tetra (Hyphessobrycon erythrostigma) and the Serpae Tetra (Hyphessobrycon eques). Social behaviour varies, with many being completely peaceful schooling fish but a few, most notably the Serpae Tetra, being nippy and somewhat aggressive towards tankmates as well as each other. The Kitty Tetra is one of the smaller species, only getting to 4 cm in length, but can be a bit nippy towards slow-loving tankmates like fancy guppies. On the other hand, these fish are very pretty, being silvery-gold in colour and marked with a black eyespot on the caudal peduncle. The Kitty Tetra is shy and likes a shady, well-planted tank. This species is collected from the Rio Xingu, and like other fish from this river system, it does best in warm, somewhat soft water conditions.

Mountain Crystal Tetra, Leptagoniates pi

This small (around 3 cm long) tetra is transparent except for the tiny black spots that cover its body and fins. It is a very peaceful fish that must be kept in a large group, at least ten specimen, to do well. Despite its small size and nervous disposition, in the right aquarium it settles down quickly and accepts finely crumbled flake foods as well as the usual live and wet-frozen foods. It must be kept away from aggressive or predatory tankmates, and is best kept as the only midwater fish. Good tankmates include small surface-dwelling species like hatchetfish, and peaceful bottom dwellers such as small Corydoras and whiptail catfish. Provide plenty of shade in the form of plants so that this species does not feel too exposed.

Rainbow Emperor Tetra, Nematobrycon lacortei

The Emperor Tetra (Nematobrycon palmeri) is reasonably widely traded and much appreciated by experienced hobbyists for use in planted community tanks. The Rainbow Emperor Tetra is essentially similar to the true Emperor Tetra, both fish being small (around 4 cm long) and sporting a bright blue band along the midline of the flank, but whereas the Emperor Tetra has blue eyes, the Rainbow Emperor Tetra has red eyes. Optimal colours only develop in a shady aquarium, and in a tank with too much direct light or a bright substrate these fish will exhibit washed out colours. Sexual dimorphism is obvious, with the males having longer fins than the females. Both species are gregarious but feisty, so while they should be kept in a group of ten or more specimens to minimise shyness, males hold small territories and sometimes chase one another. Try to keep at least equal numbers of males and females, and ideally a few more females than males will help reduce the risk of bullying. Feeding can be problematic because these tetras easily lose out against more active, fast-moving tetras and barbs, so the best tankmates are things like pencilfish and hatchetfish. Species that feed from the bottom of the tank, like Corydoras, also work well. Water chemistry isn’t critical, but avoid very hard water. These fish do best at middling temperatures, around 24 to 26 degrees C being ideal.

Sailfin Tetra, Crenuchus spilurus

The Sailfin Tetra is unusual among tetras in being a territorial rather than schooling species. As such, it’s more often kept in pairs within its own aquarium rather than a community tank, allowing about 50 litres (11 Imperial gallons) per pair. Under such conditions its interesting behaviour can be more easily observed. Males and females are strongly dimorphic, the males have stronger colours and much longer dorsal and anal fins. Males chase away other fish from their territories, which are normally centred in shady parts of the tank underneath some plants. Spawning behaviour is strikingly cichlid-like, with the male guarding the eggs until the fry become free swimming. Although often kept as just a single pair, this species will be less shy and nervous in kept in a group of three or more pairs. Sometimes the fish will school together, albeit with a hierarchy of dominance among the males, and sometimes the pairs will break away to do their own thing. Sailfin Tetras are essentially hardy, but they can be fussy about food (live and wet-frozen foods are preferred) and do need soft water to do well (aim for pH 6-7, 5-10 degrees dH). A middling to warm water temperature between 25 and 28 degrees C is recommended.

Sardina, Markiana nigripinnis

Markiana nigripinnis is a fairly large (to 15 cm) tetra from relatively cool parts of South America including Argentina and Bolivia. As such, it’s a species best suited to subtropical and low-end tropical aquaria maintained between 18 and 25 degrees C. It is also notably tolerant of a broad range of water conditions, and will do well in both soft and moderately hard water. Like a lot of the larger tetras, this species is omnivorous rather than strictly insectivorous, and alongside the usual flake and wet-frozen foods it enjoys plant materials like cooked peas and soft aquarium plants. Basic care is therefore similar to that of the more widely traded Silver Dollars. Markiana nigripinnis is a peaceful, schooling fish that is sufficiently bold and outgoing that a school of them would work well as dither fish in a tank containing peaceful, non-predatory Neotropical cichlids, oddballs or catfish of appropriate size.

Semaphore Tetra, Pterobrycon myrnae

This moderately sized tetra from Costa Rica inhabits shallow streams where the flow of water can be quite strong, so it does best in tanks with a decent water current. Unlike most other tetras this species exhibits strong sexual dimorphism. The males are smaller (around 4 cm long) than the females (which get to a little over 5 cm long). Males also sport much longer fins and have bright orange blotches of colour across their bodies. Females are essentially silvery but do have a distinctive black eyespot on the caudal peduncle. This is a completely peaceful species ideally suited to community tanks, but the males have quite long fins and should be kept away from nippy or aggressive tankmates. In terms of water chemistry it isn’t particularly demanding, though wild fish come from places where the water is slightly acidic to neutral, soft to moderately hard. It is happiest at middling temperatures between 23 and 26 degrees C.

Slender Tetra, Iguanodectes spilurus

Iguanodectes species have long, slender bodies and are adapted to fast-flowing streams. In this respect they are not good choices for the average community tank, but they could be used successfully in tanks alongside those fish that enjoy the same conditions, including danios, Corydoras catfish, suckermouth catfish and of course loaches. Iguanodectes spilurus is very widely distributed species found across tropical South America, from Ecuador to Brazil, and is consequently one of the most adaptable species in terms of water chemistry, doing well in both soft and moderately hard water. But it does need to be kept in clean, well-oxygenated water with plenty of current. Wild fish get to a maximum length of about 10 cm, but in captivity they generally stay quite a bit smaller than that. This species is silvery-gold in colour with golden band along the midline of the flank and a bold black patch on the tail fin. When kept in large groups this is a lively, peaceful species ideally suited to hillstream-type aquaria.

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