[Ebook] Encyclopedia of Aquarium & Pond Fish – Directory of Freshwater Fish – Characoids – Tetras

Directory of Freshwater Fish

Characoids

Tetras

Black Phantom Tetra (Hyphessobrycon megalopterus)

• ORIGINS: South America, where it occurs in areas of central Brazil and Bolivia.
• SIZE: 2 in (5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 73–82°F (23–28°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Social and nonaggressive

A black blotch behind the gills is a characteristic of these tetras, as is the relatively transparent body—hence the “phantom” of their common name. They look elegant in a shoal, thanks in part to the tall dorsal fin, which is more prominent in males. Include floating plants in their tank to mimic their natural habitat. Commercial breeding has made Black Phantom Tetras more tolerant in terms of their water chemistry needs, but soft, acidic conditions will give the best chance of spawning success. The eggs are scattered at random, after which the adults must be removed from the spawning tank so that they do not devour them. It takes about five days before the young are free-swimming, at which stage they should be offered a suitable fry food.

Swegles’s Tetra (Hyphessobrycon sweglesi)

• ORIGINS: Northern South America, occurring in the upper Amazon and Orinoco basins.
• SIZE: 1 1⁄2 in (4 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 68–73°F (20–23°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Peaceful and social.

Swegles’s Tetras are very sensitive to water chemistry, and their impressive red coloration will be seen clearly only under ideal conditions. They need frequent water changes and a relatively low water temperature if they are to thrive and spawn in the aquarium. A dark substrate in the spawning tank is necessary to protect their eggs from light. The female can be distinguished from the male by the white tip on the dorsal fin.

Garnet Tetra (Hemigrammus pulcher)

• ORIGINS: Northern South America, found in the Peruvian part of the Amazon River.
• SIZE: 2 in (5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 73–81°F (23–27°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Peaceful and social.

The pale-lemon background color of the Garnet Tetra contrasts with the black area on the flanks, which extends to the caudal peduncle. The body appears iridescent under subdued lighting. This fish can be sexed by the swim bladder, which is visible through the semitransparent body: it is pointed in males and rounded in females. Compatibility can be a problem when attempting to breed these fish.

Head-and-Taillight Tetra (Hemigrammus ocellifer)

• ORIGINS: Northern South America, occurring in the Amazon region, eastward as far as French Guiana.
• SIZE: 2 in (5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 75–82°F (24–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Peaceful and social.

This tetra’s rather plain body is enhanced by a red, beaconlike area on the upper eye. There is also a yellow area with a golden spot and a black blotch around the caudal peduncle. The subspecies shown here (H. O. falsus) has a black line on the tail, which is missing in other forms. A female in spawning condition lays around 300 eggs, among fine-leaved aquatic vegetation, two days after a pair is moved to the breeding tank.

Peruvian Tetra (Hyphessobrycon peruvianus)

• ORIGINS: Northern South America, in the Peruvian part of the Amazon river, in the vicinity of Iquitos.
• SIZE: 2 in (5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 73–82°F (23–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Peaceful and social.

The patterning of these tetras is variable; the black stripe that runs along the lower body is more extensive in some individuals than others. The area adjacent to this stripe is usually pale blue. Differences in coloration do not help when sexing these fish, although males tend to be more slender than females. A typical Amazonian tank is ideal for these tetras; water should be filtered through aquarium peat.

Glowlight Tetra (Hemigrammus erthyrozonus)

• ORIGINS: South America, where it occurs in the Essequibo River basin region in Guyana.
• SIZE: 1 1⁄2 in (4 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 73–82°F (23–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Peaceful and social.

The reddish-gold stripe of the Glowlight Tetra runs the entire length of its body. Males are more brightly colored than females, with a slimmer profile. During spawning, the male grips the female with its fins. If the plants in the spawning tank are too dense to allow the mating pair to swim through them with ease, many of the resulting eggs will be infertile. Up to 200 eggs are laid in total, often sinking to the substrate.

Buenos Aires Tetra (Hyphessobrycon anisitsi)

• ORIGINS: South America, in the Plate River basin of Argentina, extending to Brazil and Paraguay.
• SIZE: 4 in (10 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 64–82°F (18–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Can be aggressive

The Buenos Aires Tetra has a black stripe on its caudal fin that joins a bluish line along the side of its body. Males are more brightly colored at spawning time, while females often become aggressive toward their intended mates. Because it naturally occurs farther south than most tetras, this species can be kept at a lower water temperature in the aquarium. It will eat the leaves of aquatic plants, so avoid including delicate varieties in its tank.

Banded Rummy-Nose (Hemigrammus rhodostomus)

• ORIGINS: South America, in the lower reaches of the Brazilian Amazon, near Belem.
• SIZE: 2 in (5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 73–82°F (23–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Peaceful and social.

This species can be differentiated from the Brilliant Rummy-Nose Tetra (H. bleheri) by the patch of red on its head, which is smaller than in its close relative and does not extend to the body. Females tend to be slightly larger and more rounded than males. Aquarium breeding is possible. As with other tetras, mosquito larvae make an excellent conditioning food before the fish are transferred to the breeding tank.

BLACKWATER DWELLERS

Many wild tetras live in water that appears blackish because it contains chemicals called tannins, which result from the breakdown of leaves and other organic matter. Tannins acidify the water, and if this water chemistry is not replicated in the aquarium, the tetras may not show their vibrant coloration, and breeding will be unlikely. Adding manufactured “blackwater extract” helps to recreate the conditions under which tetras live in the wild. Peat has a similar effect on the water chemistry, as does bogwood (wood extracted from peaty surroundings). However, blackwater conditions reduce light penetration and may thus restrict plant growth.

Bleeding Heart Tetra (Hyphessobrycon erythrostigma)

• ORIGINS: Northern parts of South America, especially in the upper Amazon region.
• SIZE: 4 in (10 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 75–82°F (23–28°C); soft (50–100 mg/l) and acidic (pH 5.6–6.9).
• TEMPERAMENT: Placid, but does not breed readily.

The Bleeding Heart, so called because of the red patch on the side of its body, is one of the larger tetras. This species is not aggressive and can be kept in groups in a community aquarium, along with other placid species. Bleeding Hearts can be susceptible to fungus when introduced to the tank. To combat this, keep them at the upper end of the temperature range at first and offer food enriched with vitamin C. Over the longer term, the addition of peat to the filter will help to maintain suitable water conditions for these attractive tetras. Once established, they may live for as long as four years. Unfortunately, females are frequently reluctant to respond to the courtship of males, which are recognizable by their prominent black dorsal fin and longer anal fin.

Ulreyi Tetra (Hemigrammus ulreyi)

• ORIGINS: South America, occurring in the Paraguay River basin, south of the Amazon.
• SIZE: 2 in (5 cm).
• DIET: Eats both prepared foods and live foods.
• WATER: Temperature 75–82°F (24–28°C); soft (50–100 mg/l) and acidic to neutral (pH 6.5–7.0).
• TEMPERAMENT: Nonaggressive, shoaling fish.

This tetra is often confused with the Flag Tetra (H. heterorhabdus), from the lower Amazon basin in Brazil. The key difference is the narrow line of color above the black stripe along the body. This is orange in the Ulreyi Tetra but red in the Flag Tetra. The scales on the caudal fin are a less obvious distinguishing feature; these are missing in the Flag Tetra. This fish is named after Albert B. Ulrey, the biologist who first described it in 1895. Ulrey also discovered the X-Ray Tetra.

Rosy Tetra (Hyphessobrycon bentosi)

• ORIGINS: South America, occurring in Guyana andthroughout the lower Amazon basin.
• SIZE: 1 3⁄4 in (4.5 cm).
• DIET: Both prepared foods and small live foods.
• WATER: Temperature 75–82°F (24–28°C); soft(50–100 mg/l) and acidic to neutral (pH 6.5–7.0).
• TEMPERAMENT: Social and nonaggressive.

This tetra is often confused with the Flag Tetra (H. heterorhabdus), from the lower Amazon basin in Brazil. The key difference is the narrow line of color above the black stripe along the body. This is orange in the Ulreyi Tetra but red in the Flag Tetra. The scales on the caudal fin are a less obvious distinguishing feature; these are missing in the Flag Tetra. This fish is named after Albert B. Ulrey, the biologist who first described it in 1895. Ulrey also discovered the X-Ray Tetra.Rosy Tetras can be sexed without difficulty, since males have a longer dorsal fin that curls over at the tip, while females have a red tip on this fin. The anal fin is also longer and more concave in the male. Raising the water temperature, typically to 80°F (27°C), preceded by an increase in the live foods offered, usually stimulates spawning behavior. The fry hatch after about three days.

Lemon Tetra (Hyphessobrycon pulchripinnis)

• ORIGINS: The Amazon basin in central Brazil, South America, occurring in slow-flowing, narrow streams.
• SIZE: 2 in (5 cm).
• DIET: Prepared diets and live foods.
• WATER: Temperature 73–82°F (23–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Placid and social.

The beautiful lemon coloration of these tetras shines through only once they are well established and the water conditions become ideal. Until then, they may look rather drab. Subdued lighting, a dark substrate, and the occasional use of a color food may help to improve their appearance.

Black Neon Tetra (Hyphessobrycon herbertaxelrodi)

• ORIGINS: Distribution restricted to the Taquari River in the Mato Grosso region of Brazil.
• SIZE: 2 in (5 cm).
• DIET: Eats both prepared foods and small live foods.
• WATER: Temperature 73–81°F (23–27°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Thrives in a shoal.

In spite of its name, this species is not related to the Neon Tetra (see opposite). Females tend to be slightly larger than males, with a more rounded body shape. Breeding will be most likely if you transfer a number of these tetras as a shoal to a spawning tank, but make sure the water is softer than in the main aquarium. Live foods will help to bring the fish into breeding condition. After the eggs have been scattered among fine-leaved plants, the adult fish will need to be removed from the spawning tank.

Yellow Tetra (Hyphessobrycon bifasciatus)

• ORIGINS: South America, specifically the southeastern region of Brazil, in the vicinity of Rio de Janeiro.
• SIZE: 2 1⁄2 in (6.5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 68–77°F (20–25°C); hard (100–150 mg/l) and neutral (pH 7.0).
• TEMPERAMENT: Social and placid.

Not to be confused with the Lemon Tetra (H. pulchripinnis), the Yellow Tetra has two dark bands just behind the gills. These are most apparent in males, which are more brightly colored overall. The males also have a more concave anal fin than the females. Successful spawning is not difficult to achieve if the fish are in good condition. Fry foods intended for egg-laying species can be used for the young tetras once they are free-swimming.

Cardinal Tetra (Paracheirodon axelrodi)

• ORIGINS: Tributaries of the Rio Negro and Orinoco in the northwestern region of South America.
• SIZE: Up to 2 in (4.5 cm).
• DIET: Prepared foods, such as flake, and small live foods.
• WATER: Temperature 73–79°F (23–26°C); soft (0–50 mg/l) and acidic (pH 5.8).
• TEMPERAMENT: Social; should be kept in shoals.

One of the most beautiful of all freshwater fish, the Cardinal Tetra can have its coloration enhanced by good water conditions. It is not an easy species to breed, but the use of blackwater extract may help to encourage reproductive behavior. Cardinal Tetras need to be transferred to a separate tank for spawning purposes. The eggs hatch in about a day, with the fry becoming free-swimming about five days later.

TETRA BIOLOGY

Tetras are lively, active fish that instinctively stay close together as a shoal. A torpedolike body shape makes them suitable for the middle and upper layers of the tank. Their streamlining enables them to swim fast, which is important in the wild because their small size leaves them vulnerable to attack. They have good eyesight, however, which makes it difficult for predators to approach a shoal without being detected. Tetras can also hear underwater sounds, thanks to a connection between their swim bladder and inner ear.

Neon Tetra (Paracheirodon innesi)

• ORIGINS: Occurs only in Rio Putumayo in eastern Peru, South America.
• SIZE: 1 1⁄2 in (4 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 68–79°F (20–26°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Highly social.

These tetras are so beautiful that when they first became available to aquarists in the 1930s, they sold for the equivalent of more than a month’s wages. Today, they are likely to be found in almost every tropical fish store, being widely bred commercially. There are now even variants— including a yellow strain, christened “Mon Cheri,” and a long-finned strain—although none rivals the natural form in popularity. Neons can be easily distinguished at a glance from Cardinal Tetras (see top right), because the red stripe on their bodies is restricted to the tail region, rather than extending all along the lower body. Females tend to have plumper bodies than males, sometimes causing their stripes to look more curved. As with most other tetras, they are shoaling fish and will thrive in groups, tending to occupy the midwater region of the aquarium.

Emperor Tetra (Nematobrycon palmeri)

• ORIGINS: Northern South America, especially western parts of Colombia.
• SIZE: 3 in (7.5 cm).
• DIET: Prepared foods and live foods.
• WATER: Temperature 73–81°F (23–27°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Placid. Avoid boisterous companions.

The true purple hue of these stunning tetras will be most apparent in an aquarium with relatively subdued lighting and floating plants at the surface to diffuse the light. If the aquarium is too bright, their yellow coloration will be more dominant. Male Emperor Tetras are usually larger and more colorful than females. Provide cover on the floor of the spawning tank; otherwise, the eggs are likely to be eaten as they are laid.

Congo Tetra (Phenacogrammus interruptus)

• ORIGINS: Occurs in western Africa, in parts of the upper Congo basin.
• SIZE: 3 in (7.5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 73–82°F (23–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Highly social but nervous.

The iridescence of Congo Tetras means that their appearance can change noticeably, depending on the lighting conditions. Subdued lighting suits these fish best, helping to emphasize rather than fade their body colors. Males are larger than females and can have longer fins, which may be ragged on occasions. Do not mix these fish with fin-nipping species, since this can lead to serious problems. It is possible to persuade pairs of Congo Tetras to spawn, but you will have more chance of success if you have a small shoal, since these fish normally reproduce in a group. Adding blackwater extract to the water to raise the tannic acid level will also help. The female may produce as many as 300 eggs, typically quite early in the morning, which will then take about five days to hatch.

Jelly Bean Tetra (Ladigesia roloffi)

• ORIGINS: The Yung River in West Africa, occurring in Sierra Leone, Liberia, Ghana, and Ivory Coast.
• SIZE: 1 1⁄2 in (4 cm).
• DIET: Eats prepared foods and small live foods.
• WATER: Temperature 72–79°F (22–26°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Placid shoaler.

Jelly Bean Tetras are so called because of their size and shape. One of the less commonly encountered tetra species, they are not difficult to keep, as long as the aquarium’s water chemistry is very similar to that which they encounter in the wild. Fading of the red from their fins is a sign that conditions are less than ideal. The tank must be covered, because Jelly Bean Tetras can jump well, and it should include floating plants to give shade. Pairs will spawn on a layer of aquarium peat.

Sailfin Tetra (Crenuchus spilurus)

• ORIGINS: Northern South America, occurring in Guyana and the middle Amazon.
• SIZE: 2 1⁄2 in (6 cm).
• DIET: Fresh and thawed live foods preferred.
• WATER: Temperature 75-82°F (24–28°C); soft (50–100 mg/l) and acidic (pH 6.0).
• TEMPERAMENT: Keep singly or in pairs.

Sexing these tetras is simple; males are larger and have more prominent dorsal fins than females. Sailfins are predators. They usually eat invertebrates, but they consume any smaller fish sharing their tank, especially fry. Pairs spawn seasonally on flat rocks in the wild, guarding the eggs until they hatch and wafting water over them with their ventral fins.

LIFE SPANS IN AQUARIUMS

Most aquarium fish live longer than their wild counterparts, provided they are correctly housed and fed. Modern diets have reduced the risks of nutritional diseases that could reduce their life span, and aquarium fish will not be at risk from predators if their tankmates are carefully chosen. This enables small fish such as tetras to come close to attaining their maximum life span. Members of the Nematobrycon genus, such as these Emperor Tetras, are typically the longest-lived tetras, living for up to six years in aquariums.

African Red-Eyed Characin (Arnoldichthys spilopterus)

• ORIGINS: West Africa, ranging from Lagos, Nigeria, to the Niger Delta.
• SIZE: 4 in (10 cm).
• DIET: Eats prepared foods and live foods.
• WATER: Temperature 73–82°F (23–28°C); hard (150–200 mg/l) and neutral (pH 7.0).
• TEMPERAMENT: Placid shoaler.

Both sexes show the characteristic red eye marking, but they can usually be sexed on the basis of the anal fin. In the males, this is convex and more colorful, displaying red, yellow, and black bands. The extremely active nature of African Red-Eyed Characins precludes dense planting in their tank. Pairs can be prolific, with females producing more than 1,000 eggs at a single spawning. A soft base in the spawning tank is vital, since the fry will dive to the bottom if scared. They grow fast, reaching almost 2 in (5 cm) in length within seven weeks.

Blue Emperor (Inpaichthys kerri)

• ORIGINS: South America. A relatively recent discovery nfrom the Rio Aripuana in Amazonia.
• SIZE: 2 in (5 cm).
• DIET: Eats both prepared diets and small live foods.
• WATER: Temperature 75–81°F (24–27°C); soft (50–100 mg/l) and neutral (pH 7.0).
• TEMPERAMENT: Placid.

The stunning blue of the adult male, seen below, is maintained only in good water conditions. The female is smaller and duller, with brownish-yellow upperparts and a broad black band passing through the eyes and along the body. These fish need a well-planted tank with an open area for swimming. They are best kept in groups and are perfect for a community aquarium, making ideal companions for nonaggressive species such as corydoras catfish.

X-Ray Tetra (Pristella maxillaris)

• ORIGINS: South America, in Venezuela, Guyana, and the lower Amazon in Brazil.
• SIZE: 1 3⁄4 in (4.5 cm).
• DIET: Prepared foods and live foods.
• WATER: Temperature 73–82°F (23–28°C); soft (50–100 mg/l) and acidic to neutral (pH 6.0–7.0).
• TEMPERAMENT: Nonaggressive.

The transparent appearance of X-Ray Tetras allows them to be sexed on the basis of the shape of their swim bladder, which is more pointed in the males. Despite their transparency, they are not colorless, with the golden, red, white, and black areas on their bodies giving rise to their alternative name of Water Goldfinch. The coloration of X-Ray Tetras can be emphasized if they are kept in an aquarium with a dark base and subdued lighting.

Yellow-Banded Tetra (Moenkhausia sanctaefilomenae)

• ORIGINS: South America, occurring in eastern Peru and Bolivia, Paraguay, and western Brazil.
• SIZE: 3 in (7.5 cm).
• DIET: Eats both prepared foods and live foods.
• WATER: Temperature 73–82°F (23–28°C); hard (100–150 mg/l) and neutral (pH 7.0).
• TEMPERAMENT: Has a strong shoaling instinct.

Attention is immediately drawn to the head of this fish by the red on the upper part of the iris. The yellow band on the caudal peduncle distinguishes it from the larger and more aggressive Glass Tetra (M. oligolepsis). Yellow-Banded Tetras are active fish, so their tank should have planted areas around the sides and to the rear for use as retreats and a clear area at the front for swimming. These fish are quite adaptable in terms of their water chemistry requirements. Sexing is difficult unless the fish are in breeding condition, when females appear swollen with spawn. The spawning tank must be densely planted to deter the fish from eating their own eggs. The female scatters several hundred eggs in vegetation, often among the roots of floating plants. The adults will then need to be removed. The young emerge after about two days; by a week old, they should be large enough to be weaned off fry foods and onto brine shrimp.

One-Lined African Tetra (Nannaethiops unitaeniatus)

• ORIGINS: Equatorial Africa, occurring in the Niger, Congo, and Nile Rivers.
• SIZE: 3 in (7.5 cm).
• DIET: Prepared foods, live foods, and vegetable matter.
• WATER: Temperature 73–79°F (23–26°C); soft (50–100 mg/l) and neutral (pH 7.0).
• TEMPERAMENT: Placid and social.

In this species, the sexes may be distinguished only when the fish are in spawning condition; at this time, males develop red areas on the upper part of the caudal fin and on the square-shaped dorsal fin. The odd, jerky swimming motion of these tetras is perfectly normal. Provide fine-leaved plants in the spawning tank, among which females will lay up to 500 eggs. Hatching takes two days, and the fry are free-swimming five days later.

Croaking Tetra (Mimagoniates microlepis)

• ORIGINS: Southern South America, distributed throughout southeastern Brazil.
• SIZE: 2 1⁄4 in (5.5 cm).
• DIET: Flake and small live foods.
• WATER: Temperature 66–77°F (19–25°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Placid and social.

The soft blue coloration of these tetras is especially apparent in males, which are slightly larger than females and have longer fins when full-grown. Males are unusual in that they attract females by releasing chemical messengers called pheromones from a gland located at the base of the caudal fin. Live foods such as mosquito larvae are a valuable conditioning food; the tetras subsequently spawn among vegetation. Croaking Tetras can make croaking sounds via their air bladder.

Argentine Bloodfin (Aphyocharax anisitsi)

• ORIGINS: Southern South America, where it is restricted to the Rio Parana in Argentina.
• SIZE: 2 in (5 cm).
• DIET: Flake and small live foods.
• WATER: Temperature 64–82°F (18–28°C); soft (50–100 mg/l) and around neutral (pH 7.0).
• TEMPERAMENT: Placid and social.

The blood-red coloration on the fins of this tetra is not a consistent feature and is more pronounced in some individuals than others. Male fish have a hook on their anal fin. Pairs spawn quite readily among vegetation, but the adults will rapidly eat the eggs, numbering several hundred, if they get the chance. Argentine Bloodfins are easy to keep and have a life expectancy of more than 10 years

Ansorge’s Neolebias (Neolebias ansorgii)

• ORIGINS: Central equatorial Africa, where it is found in shallow pools in Angola and Cameroon.
• SIZE: 1 1⁄2 in (3.5 cm).
• DIET: Flake and small live foods.
• WATER: Temperature 75–82°F (24–28°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Placid and social.

Although this is the most colorful fish in its genus, it has never been very popular with aquarists. Unusually for a characoid, Ansorge’s Neolebias lacks an adipose fin. The more brightly colored male, pictured below, has a reddish-orange body, with a darker stripe along the side and a black spot at the base of the tail. This coloration is improved by subdued lighting conditions and a dark base in the aquarium. Ansorge’s Neolebias is best kept in a single-species tank. It naturally inhabits shallow pools, so make sure the water is no more than 8 in (20 cm) deep. The breeding tank should have a peat-covered base, on which the fish will spawn. Hatching occurs within a day, and the young will need a fry food at first. The new generation will be ready to breed when the fish are seven months old.

Blind Cave Tetra (Astyanax mexicanus)

• ORIGINS: Central America, restricted to the San Luis Potosi region of Mexico.
• SIZE: 3 1⁄2 in (9 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 64–82°F (18–28°C); hard (100–150 mg/l) and alkaline (pH 7.5).
• TEMPERAMENT: Placid and social.

Blind because they live in darkness in the wild, these fish should be kept in an aquarium decorated with slate, devoid of plants, and lit by a nighttime fluorescent tube. A single-species setup is preferable, and some vegetable matter should be provided in the diet. Eggs will be scattered over a suitable spawning mop, after which the

Small-Mouth Featherfin Tetra (Bryconaethiops microstoma)

• ORIGINS: Central equatorial Africa, occurring in Stanley Pool, lower Zaire, in fast-flowing water.
• SIZE: 6 in (15 cm).
• DIET: Flake, small live foods, and algae.
• WATER: Temperature 75–82°F (24–28°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Placid, but does not shoal.

The long trailing filaments on the dorsal fin are seen only in the male Small-Mouth Featherfin, shown here; in the female, the dorsal fin is shorter and more rounded. Young Small-Mouth Featherfins have a silvery body color, which darkens with age. The water chemistry requirements of Small-Mouth Featherfins are quite specific; the water must be well oxygenated, with good movement to replicate the fast-flowing stretches of water that they inhabit in the wild. Being rather nervous fish, they need a well-planted tank to provide plenty of hiding places. The tank should also be covered, because they are excellent jumpers. Although algae form an important part of their natural diet, they will often ignore alternative plant foods offered to them. Small-Mouth Featherfins have an unusually small mouth compared to other tetras and so should only be offered live foods of an appropriate size.

Glass Bloodfin (Prionobrama filigera)

• ORIGINS: South America, occurring in central and southern Brazil, Paraguay, and Argentina.
• SIZE: 2 1⁄2 in (6 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 72–86°F (22–30°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Placid and social.

When backlit, the body of the Glass Bloodfin is completely transparent. Sexing is straightforward, because only mature males display a white extension of the outer edge of the anal fin. An aquarium for Glass Bloodfins should be shaded and incorporate floating plants and retreats around the sides. These active fish must also have plenty of space in which to swim. When spawning, Glass Bloodfins scatter their eggs among clumps of vegetation. The eggs hatch about three days later.

ADAPTED TO LIFE UNDERGROUND

The Blind Cave Tetra (see opposite) occurs only in a single Mexican cave system. Outside, in nearby rivers, the ancestral form of this fish can still be found, complete with natural pigmentation and fully functional eyes. Reflecting their origins, Blind Cave Tetras can see when they hatch but lose vision as skin grows over the eyes. This happens even when they are reared in a well-lit environment. The principal sensory input of these fish comes from the lateral line system, which runs along each side of the body. This detects changes in water movements. Blind Cave Tetras probably also have a good sense of smell, because they have no problem finding enough food when competing with fully sighted species in aquarium surroundings.

False Silver-Tipped Tetra (Hasemania nana)

• ORIGINS: South America, in the Rio Purus tributaries in western Brazil and the San Francisco basin in the east.
• SIZE: 2 in (5 cm).
• DIET: Prepared foods and small live foods.
• WATER: Temperature 72–82°F (22–28°C); soft (50–100 mg/l) and acidic (pH 6.5).
• TEMPERAMENT: Placid and social.

A coppery body and contrasting silver tips on the fins, including both lobes of the caudal fin, typify the males of this small, shoaling species. Females have a paler, silvery-gold coloration, as well as a more rounded body shape, which is most obvious when they are in spawning condition. A separate spawning tank is needed to prevent the eggs from being devoured. Hatching takes place in a day; the free-swimming young require fry foods at first.

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