African Red Eye Tetra

Quick summary

The African Red Eye Tetra is a hardy, easy-to-keep, peaceful shoaling fish that’s great for beginners, but it needs a fairly large tank of at least 200 litres and should be kept in groups of six or more. If you can provide the space, it’s a low-maintenance, colourful addition to a community tank with similarly sized, non-aggressive tank mates.

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In this guide:

• Introduction
• Quick Stats
• Appearance
• Natural Habitat
• Tank Size and Setup
• Water Parameters
• Filtration and Equipment
• Diet and Feeding
• Behaviour and Temperament
• Tank Mates
• Breeding
• Common Diseases
• FAQs

Introduction

The African Red Eye Tetra (Arnoldichthys spilopterus) is one of the most visually striking yet underappreciated tetras available to freshwater aquarists. Native to the coastal river systems of West Africa, this species stands apart from its South American relatives with its large, shimmering scales, bold red eye, and lively disposition. Despite being a member of the family Alestidae rather than the Characidae that most hobbyists associate with tetras, the African Red Eye Tetra shares many of the same appealing qualities – it is a peaceful, active shoaling fish that brings constant movement and sparkle to the mid-water column of any suitably sized aquarium.

First described by Boulenger in 1909, the species has been available in the aquarium trade for many decades, yet it remains somewhat overlooked in favour of smaller, more commonly stocked South American tetras such as neons and cardinals. This is somewhat unfortunate, as the African Red Eye Tetra is a robust and hardy fish that rewards attentive care with exceptional coloration and engaging group behaviour. Adults develop large, iridescent scales that catch the light beautifully, shifting through hues of green, gold, and copper depending on the viewing angle and ambient lighting. The namesake red eye provides a vivid focal point, especially when a group of these fish is swimming in unison.

At a mature size of around 8 to 9 centimetres, the African Red Eye Tetra is considerably larger than many popular tetra species, and this must be taken into account when planning tank size and selecting companions. It is an active swimmer that appreciates open space and the security of a group, making it ideal for medium to large community aquariums with other peaceful fish of similar size. This care guide covers everything you need to know to keep this magnificent African tetra thriving in your aquarium, from water parameters and tank setup to breeding, diet, and compatible tank mates.

Appearance

The African Red Eye Tetra is a genuinely handsome fish that only truly reveals its full beauty once settled in a well-maintained aquarium with appropriate lighting. The body shape is typical of the larger African tetras – laterally compressed, somewhat elongated, and deep-bodied compared to the slender profiles of many South American species. Adults commonly reach 8 to 9 centimetres in standard length, making them one of the larger tetra species commonly available in the hobby.

The most immediately striking feature is, of course, the vivid red iris that gives the species its common name. This crimson eye stands out sharply against the silver-gold base coloration of the body and provides an unmistakable identification mark. The eye colour intensifies as the fish matures and is generally brightest in healthy, well-fed specimens kept in optimal water conditions.

The body is covered in large, highly reflective scales that produce an extraordinary shimmering effect. Under aquarium lighting, the flanks can flash green, gold, copper, and even subtle blue tones as the fish moves. This iridescence is most pronounced along the lateral line and upper body. A faint dark horizontal stripe may be visible along the midline, though this is often obscured by the overall shimmer of the scales. The dorsal surface is typically olive to brownish-green, grading into brighter silver and gold tones on the flanks, with a paler, sometimes whitish belly.

Males and females can be distinguished with reasonable reliability in mature specimens. Males tend to be slimmer and slightly more intensely coloured, with a more pronounced red and orange blotch on the anal fin. The anal fin of the male may also show dark banding or a darker leading edge. Females are generally fuller-bodied, particularly when carrying eggs, and their anal fin coloration is typically less vivid, often appearing more uniformly clear or with only subtle markings. The dorsal fin of both sexes carries a dark blotch, which is a characteristic feature of the species.

Juvenile specimens are considerably less colourful than adults and may appear rather plain silver with only a hint of the red eye developing. Patience is required, as the full coloration typically develops over the first year of life, with the iridescent scaling becoming increasingly impressive as the fish grows.

Natural Habitat

Arnoldichthys spilopterus is found in the coastal river systems and lagoons of West Africa, primarily in Nigeria and Benin. Its range centres on the Lagos Lagoon system, the lower Niger Delta region, and the Ogun River basin. These are lowland tropical waterways characterised by warm temperatures, moderate to slow flow, and a mix of open water and vegetated margins.

In its natural environment, the African Red Eye Tetra inhabits rivers, streams, and associated lagoons where the water is often slightly acidic to neutral, soft to moderately hard, and frequently stained with tannins from decomposing organic matter. The substrate in these habitats is typically composed of sand, mud, and leaf litter, with overhanging vegetation providing dappled shade. Fallen branches, submerged roots, and marginal plants create structure within the water column, offering both shelter and foraging opportunities.

The species is found in areas with relatively warm water, as would be expected for a tropical West African fish. Temperatures in its natural range typically fall between 24 and 28 degrees Celsius throughout the year, with little seasonal variation. The water chemistry in these coastal lowland systems can be variable, influenced by rainfall, tidal effects near the coast, and the degree of vegetative decay in the water. This natural adaptability to a range of conditions is one reason why the African Red Eye Tetra proves to be a relatively hardy and undemanding aquarium fish.

In the wild, these fish form shoals that move through the mid-water and upper water columns, feeding on insects, small invertebrates, and organic debris. They are often found alongside other African characins, cichlids, and catfish species, occupying a niche as mid-water planktivores and opportunistic feeders. Understanding this natural context helps inform appropriate aquarium conditions, particularly the need for open swimming space, a group social structure, and a varied diet.

Tank Size and Setup

Given its adult size of 8 to 9 centimetres and its active swimming nature, the African Red Eye Tetra requires a reasonably spacious aquarium. A minimum tank size of 200 litres is recommended, and this should be considered the starting point for a group of six to eight individuals. Larger tanks of 300 litres or more are preferable, particularly if you wish to keep a larger shoal or house them in a community setting with other species. The tank should ideally be at least 100 centimetres in length to provide adequate horizontal swimming room, as these fish are active and cover a lot of ground during their daily movements.

The aquascape should balance open swimming areas with structured zones for shelter and visual interest. A sandy or fine gravel substrate works well and reflects the natural habitat. Driftwood and bogwood pieces provide both aesthetic appeal and functional hiding spots, while also releasing tannins that can slightly soften and acidify the water – conditions that the African Red Eye Tetra appreciates. If you choose to add leaf litter such as Indian almond leaves or oak leaves, these will further replicate natural conditions and provide a subtle tannin stain to the water.

Live plants are a welcome addition and help to create a natural-looking environment. Hardy species such as Anubias, Java Fern, Vallisneria, and Amazon Swords are all suitable choices. Floating plants can be used to diffuse overhead lighting, which can help to bring out the iridescent colours of the fish and make them feel more secure. However, ensure that the planting does not encroach too heavily on the open mid-water swimming space that this active species requires.

A secure, tight-fitting lid is advisable. Like many active tetra species, the African Red Eye Tetra is capable of jumping, particularly when startled or during the initial settling-in period. Ensuring there are no gaps in the hood or cover will prevent unfortunate losses.

Lighting should be moderate. Overly bright lighting can cause the fish to appear washed out and may make them more skittish. Moderate lighting, particularly when supplemented with floating plants to create shaded areas, will showcase the iridescent scales to their best advantage and encourage natural behaviour.

Water Parameters

The African Red Eye Tetra is a relatively adaptable species when it comes to water chemistry, tolerating a reasonable range of parameters. However, stability is always more important than chasing a specific number, so aim to maintain consistent conditions within the recommended ranges. Regular water changes of 20 to 30 per cent weekly will help to maintain good water quality and stable parameters.

While the species can tolerate a broad range of conditions, slightly acidic to neutral water in the pH range of 6.5 to 7.0 with moderate hardness tends to produce the best coloration and overall health. Elevated nitrate levels should be avoided, as prolonged exposure to high nitrates can suppress the immune system and dull coloration. A well-maintained aquarium with regular partial water changes and efficient biological filtration will keep these parameters within safe limits without difficulty.

Water temperature should ideally be kept in the range of 24 to 27 degrees Celsius for day-to-day keeping. The species can tolerate temperatures towards the extremes of its range for short periods, but sustained temperatures below 23 degrees or above 28 degrees Celsius are best avoided. A reliable aquarium heater with a thermostat is essential to maintain a stable temperature, particularly in cooler climates or rooms subject to temperature fluctuations.

Filtration and Equipment

Good filtration is essential for keeping African Red Eye Tetras in excellent health. As active, medium-sized fish kept in groups, they produce a moderate bioload that requires efficient biological, mechanical, and chemical filtration. An external canister filter is the preferred choice for tanks of 200 litres and above, as these provide high-capacity media chambers and reliable flow rates without taking up internal tank space. For tanks in the 200 to 300 litre range, a filter rated for at least 800 to 1,000 litres per hour of turnover is a reasonable target.

While the African Red Eye Tetra does not require strong currents – indeed, very high flow can cause stress and fatigue – it does appreciate some water movement. Position the filter outlet to create gentle to moderate flow across the length of the tank, replicating the slow-moving rivers and streams of its natural habitat. A spray bar can be useful for distributing flow evenly and preventing any excessively strong current in one area.

A thermostatically controlled heater is essential to maintain stable tropical temperatures. Choose a heater rated appropriately for your tank volume – as a general rule, 1 watt per litre is a common guideline, though this varies depending on room temperature and tank insulation. In larger tanks, two smaller heaters placed at opposite ends can provide more even heating and offer redundancy in case one unit fails.

Lighting should be moderate in intensity. LED lighting systems with adjustable brightness and colour temperature are ideal, as they allow you to fine-tune the light levels to suit the fish and any live plants in the aquarium. A colour temperature in the range of 6,500 to 7,000 Kelvin works well for planted tanks and also shows off the iridescent scales of the African Red Eye Tetra effectively. A timer should be used to maintain a consistent photoperiod of 8 to 10 hours per day.

An air pump is not strictly necessary if filtration provides adequate surface agitation for gas exchange, but one can be useful during warmer months when dissolved oxygen levels may drop. A thermometer – ideally a digital one for accuracy – should be used to monitor water temperature continuously. A quality liquid test kit for monitoring ammonia, nitrite, nitrate, and pH is invaluable, particularly during the initial stocking period and when making any changes to the tank.

Diet and Feeding

The African Red Eye Tetra is an omnivorous species with a hearty appetite and few dietary challenges. In the wild, it feeds on a varied diet of insects, small crustaceans, worms, and organic debris found in the water column and at the surface. In captivity, it readily accepts a wide range of foods, and providing dietary variety is the key to maintaining excellent health, vibrant coloration, and natural behaviour.

A high-quality flake or granule food formulated for tropical fish should form the staple of the diet. Choose products with a high protein content and minimal fillers. Granules or micro-pellets that float or sink slowly are particularly well-suited, as they allow the fish to feed naturally in the mid-water column. Flake food is also accepted readily, though it can sometimes be consumed too quickly at the surface without all members of the group getting a fair share.

Regular supplementation with live and frozen foods is highly recommended and will bring out the best in this species. Bloodworm, daphnia, brine shrimp, mosquito larvae, and tubifex are all excellent choices. Live foods in particular stimulate natural hunting and foraging behaviour and are often eagerly pursued by the shoal. Frozen alternatives are a convenient and safe option that provides similar nutritional benefits. Offer these supplementary foods two to three times per week alongside the staple diet.

Vegetable matter should also be included in the diet to some extent. Spirulina-enriched flakes or granules, blanched spinach, or blanched peas can be offered occasionally to ensure a balanced nutritional intake. Many quality tropical flake foods already contain some vegetable and algal content, which helps to meet this need.

Feed small amounts two to three times daily rather than one large feeding. This approach more closely mimics natural feeding patterns, reduces waste, and ensures that all members of the group have the opportunity to feed. Each feeding should be consumed within two to three minutes – if food remains uneaten after this time, reduce the quantity at subsequent feedings.

Behaviour and Temperament

The African Red Eye Tetra is a peaceful, active, and sociable species that is best appreciated when kept in a group. Shoaling is a fundamental aspect of its natural behaviour, and this fish should always be kept in groups of six or more individuals. Larger groups of eight to twelve or more are preferable, as they encourage more natural behaviour patterns, reduce stress, and result in a more impressive visual display as the fish move together through the water column.

In a suitably sized group, African Red Eye Tetras spend much of their time swimming actively in the mid-water to upper water column, moving in loose formation and occasionally coming together into a tighter shoal, particularly when startled or when feeding. Their large, reflective scales create a mesmerising shimmering effect as the group moves, especially under moderate lighting. Individual fish may also explore the tank independently, investigating decorations, plants, and the substrate.

This species is generally peaceful towards other fish and is not known for fin-nipping or territorial aggression. Some minor chasing and jostling may occur within the group, particularly among males establishing a social hierarchy, but this is normal behaviour and rarely results in any harm. Providing adequate space and maintaining a group of the appropriate size will minimise any issues.

Keeping African Red Eye Tetras in groups smaller than six is not recommended, as individuals kept singly or in very small numbers often become stressed, skittish, and may exhibit abnormal behaviour such as hiding, loss of appetite, or increased susceptibility to disease. A stressed fish that lacks the security of a group will also display much poorer coloration than one kept in appropriate social conditions.

The species can be somewhat nervous during the initial acclimation period, and new specimens may hide or dart around the tank when approached. This behaviour typically subsides within a few days to a couple of weeks as the fish settles in. Maintaining a calm environment, providing some cover, and avoiding sudden movements near the tank will help to speed up the settling process. Once established, they become confident and engaging aquarium inhabitants.

Tank Mates

The African Red Eye Tetra’s peaceful nature and moderate adult size make it a versatile community fish that can be housed with a wide variety of similarly tempered species. The key considerations when selecting tank mates are temperament, size compatibility, and shared water parameter requirements. Avoid very small species that could potentially be viewed as food, and steer clear of aggressive or highly territorial fish that might bully or stress the tetras. Fast-moving fin-nippers should also be avoided, as the African Red Eye Tetra’s large, shimmering fins can attract unwanted attention.

Good tank mates

• Congo Tetra – A fellow African tetra of similar size and temperament, creating a stunning and geographically appropriate pairing.
• Kribensis – A peaceful West African dwarf cichlid that occupies the lower tank levels, complementing the mid-water swimming habits of the Red Eye Tetra.
• Bristlenose Pleco – A hardy bottom-dwelling algae eater that stays out of the tetra’s way and shares similar water parameter preferences.
• Corydoras Catfish – Peaceful bottom dwellers that make excellent companions and help to keep the substrate clean.
• Pearl Gourami – A calm, medium-sized gourami that coexists peacefully and adds visual variety to the community.
• Rainbowfish – Active, similarly sized shoaling fish that share the mid-water column and complement the tetra’s display beautifully.
• African Butterfly Fish – A surface-dwelling species from the same geographic region that peacefully occupies a different zone of the tank.
• Synodontis Catfish – Hardy African catfish that are generally peaceful and provide an interesting contrast in the lower areas of the aquarium.

Fish to avoid

• Oscar – A large, predatory cichlid that will readily eat African Red Eye Tetras as they grow.
• Tiger Barb – A notorious fin-nipper that can harass and stress the tetras, particularly targeting their flowing fins.
• Jack Dempsey – An aggressive cichlid far too large and territorial to be housed with peaceful tetras.
• Red Tail Shark – Can become highly territorial and aggressive, chasing and stressing mid-water swimmers.
• Flowerhorn – An extremely aggressive hybrid cichlid that is incompatible with virtually all community fish.
• Green Terror – A large, aggressive South American cichlid that would dominate and potentially harm the tetras.
• Neon Tetra – While peaceful, neon tetras are small enough to potentially be consumed by fully grown African Red Eye Tetras.
• Bucktooth Tetra – Despite being a tetra, this species is a scale-eater and will attack and damage tank mates.

Breeding

Breeding the African Red Eye Tetra in captivity is achievable but requires some dedicated preparation. The species is an egg-scattering spawner that does not exhibit any parental care, and both adults will readily consume their own eggs if given the opportunity. For this reason, a separate breeding tank is strongly recommended.

To condition breeding pairs or groups, increase the frequency and quantity of high-quality live and frozen foods over a period of two to four weeks. Bloodworm, daphnia, and brine shrimp are particularly effective conditioning foods. Well-conditioned females will become noticeably fuller in the body as they develop eggs, while males will display intensified coloration, particularly in the anal fin region.

The breeding tank should be set up with soft, slightly acidic water – a pH of 6.0 to 6.5 and a GH of 3 to 6 dGH is ideal. Temperature should be raised slightly to the upper end of the species’ range, around 26 to 28 degrees Celsius. The tank should be dimly lit, as bright lighting can inhibit spawning behaviour. A layer of fine-leaved plants such as Java Moss or spawning mops should be provided to catch the scattered eggs. Alternatively, a mesh grid placed above the base of the tank can prevent the adults from reaching fallen eggs.

Spawning typically occurs in the morning and is preceded by vigorous chasing and displaying by the male. The pair will swim closely together, with the female releasing batches of eggs that are fertilised by the male as they scatter among the plants or fall to the substrate. A single spawning event can produce 200 to 500 or more eggs. Once spawning is complete, the adults should be removed from the breeding tank immediately to prevent egg predation.

The eggs are small, clear to slightly amber in colour, and will hatch within approximately 24 to 36 hours at the recommended temperature. The resulting fry are very small and will initially survive on their yolk sac for the first couple of days. Once free-swimming, they should be fed infusoria or commercially available liquid fry food for the first week, before being gradually transitioned to newly hatched brine shrimp (Artemia nauplii) and microworms. Growth is relatively slow initially, and the fry require clean water and frequent small feedings to develop properly. Regular partial water changes with matched temperature and chemistry are essential during the rearing phase.

Common Diseases

The African Red Eye Tetra is a generally robust species that is not particularly prone to any species-specific diseases. However, like all freshwater aquarium fish, it can be affected by common ailments if water quality deteriorates, if the fish is stressed, or if pathogens are introduced to the tank. Prevention through good husbandry practices is always preferable to treatment.

White Spot Disease (Ichthyophthirius multifiliis), commonly known as Ich, is one of the most frequently encountered diseases in freshwater aquaria. It presents as small white spots resembling grains of salt on the body, fins, and gills. Affected fish may also flash against hard surfaces, clamp their fins, and become lethargic. Ich is typically triggered by temperature fluctuations or stress and can be treated effectively by gradually raising the water temperature to 28 to 30 degrees Celsius and using a proprietary white spot treatment. Early intervention is important, as the disease can spread rapidly through a tank.

Fin rot is a bacterial infection that causes the edges of the fins to become ragged, discoloured, and progressively eroded. It is almost always secondary to poor water quality, physical injury, or stress. Treatment involves addressing the underlying cause – typically through improved water quality via water changes and filter maintenance – and, in more advanced cases, the use of an antibacterial medication.

Fungal infections may occasionally occur, appearing as white or grey cottony growths on the body or fins. These are often opportunistic, developing on damaged tissue or in conjunction with other diseases. Anti-fungal treatments are available and are generally effective when used promptly.

Internal parasites can sometimes affect African Red Eye Tetras, particularly wild-caught specimens. Symptoms may include weight loss despite normal feeding, a hollow belly, white or stringy faeces, and general lethargy. Dedicated anti-parasitic medications are available for treating these conditions and should be used according to the manufacturer’s instructions.

Quarantining all new fish for a minimum of two to four weeks before introducing them to an established tank is one of the most effective ways to prevent the introduction of disease. During the quarantine period, observe the new arrivals closely for any signs of illness and treat if necessary before they come into contact with your existing stock.

Maintaining excellent water quality through regular water changes, avoiding overfeeding, ensuring stable water parameters, and minimising stress are the cornerstones of disease prevention. A well-maintained tank with appropriate stocking levels and good nutrition will rarely experience significant disease outbreaks.

FAQs

How many African Red Eye Tetras should I keep together?

A minimum group of six is essential, but eight to twelve or more is strongly recommended. Larger groups encourage natural shoaling behaviour, reduce individual stress, and produce a far more impressive visual display. Keeping fewer than six individuals can result in skittish, stressed fish that fail to display their natural coloration and behaviour patterns. If your tank is large enough, always err on the side of a bigger group.

Are African Red Eye Tetras suitable for beginners?

Yes, the African Red Eye Tetra is considered an easy species to keep and is well-suited to beginners who have a suitably sized, fully cycled aquarium. The species is hardy, tolerant of a reasonable range of water parameters, and not fussy about food. The main consideration for beginners is the need for a tank of at least 200 litres, which is larger than many starter setups. Provided this space requirement is met and basic maintenance routines are followed, this is an excellent species for aquarists at any experience level.

Will African Red Eye Tetras eat smaller fish?

While the African Red Eye Tetra is a peaceful species, it is a medium-sized fish with a relatively large mouth for a tetra. Very small fish such as neon tetras, microrasboras, or newborn fry could potentially be consumed, particularly by fully grown adults. It is best to choose tank mates that are at least 4 centimetres in length as adults to avoid any risk. The species is not actively predatory towards other fish, but its size means that very small companions should be avoided as a precaution.

Do African Red Eye Tetras need a planted tank?

While a planted tank is not strictly necessary, live plants are highly beneficial and recommended. Plants provide visual barriers that reduce stress, create a more natural environment, help to maintain water quality by absorbing nitrates, and can diffuse lighting to bring out the best coloration in the fish. Hardy, low-maintenance plants such as Java Fern, Anubias, and Vallisneria are all excellent choices. The most important aspect of the tank setup, however, is providing sufficient open swimming space alongside any planted areas.

Why are my African Red Eye Tetras hiding and not showing colour?

This behaviour is most commonly seen in newly introduced specimens that are still acclimating to their environment. Stress from transport, a new tank, or insufficient group size can cause the fish to hide and display pale, washed-out coloration. Ensure that you are keeping them in a group of at least six, that the tank has some cover in the form of plants or driftwood, and that the lighting is not excessively bright. Given time – typically one to three weeks – and stable, good-quality water conditions, the fish should settle in, become more confident, and begin to display their full coloration. A varied diet rich in live and frozen foods will also help to enhance their colour.

Related Guides

• Congo Tetra Care Guide – Another stunning African tetra species that makes an excellent companion and shares similar care requirements.
• Kribensis Care Guide – A popular West African dwarf cichlid that pairs beautifully with African Red Eye Tetras in a community setup.
• African Butterfly Fish Care Guide – A unique surface-dwelling African species that can be housed alongside African Red Eye Tetras.
• Synodontis Catfish Care Guide – Hardy African catfish that complement an African-themed community aquarium.
• Rainbowfish Care Guide – Active, colourful shoaling fish of similar size that share many of the same community tank requirements.