What the African Red Eye Tetra Is and Where It Comes From

The African Red Eye Tetra (Arnoldichthys spilopterus) is a small schooling fish native to West Africa, primarily the Niger River basin in Nigeria and Cameroon. It grows to about 2 inches long and gets its name from the distinctive red or orange coloring around its eye, which becomes more vivid in healthy, well-fed fish. The body is silvery with a dark stripe running along the lateral line, and the dorsal and anal fins often show red or yellow tints.

This species has been a staple in the aquarium hobby for decades because it is hardy, peaceful, and visually striking in groups. Unlike many tetras, the African Red Eye is less aggressive toward tankmates and tolerates a wider range of water conditions, making it forgiving for hobbyists still learning the basics of freshwater fishkeeping.

Key Takeaways

  • African Red Eye Tetras must be kept in groups of at least six to eight fish, as they are schooling fish and become stressed or aggressive when isolated or in pairs.
  • A 20-gallon long tank is the practical minimum for a small school, with an additional 2 to 3 gallons per fish as the group grows.
  • They prefer slightly acidic to neutral water between 72 and 82 degrees Fahrenheit and do well in tanks with plants, driftwood, and moderate lighting.
  • Feed a mix of high-quality flake food, small pellets, and occasional live or frozen foods like brine shrimp to bring out their red coloring.
  • Breeding in captivity is possible but requires patience; fry are small and need infusoria or liquid fry food for the first few days.

Tank Size and Setup for a School

A single African Red Eye Tetra should never be kept alone. These fish are schooling fish and become stressed, hide constantly, or display aggression toward other fish when kept in pairs or small numbers. Start with a group of six to eight fish minimum; a 20-gallon long tank is the practical floor for this size school. If you plan to keep more than eight, add 2 to 3 gallons per additional fish.

The tank benefits from moderate to dense planting—live plants like Amazon sword, anubias, and Java fern provide shelter and help stabilize water chemistry. Add driftwood or smooth rocks to create visual breaks and resting spots. These fish are not aggressive diggers, so substrate can be sand or fine gravel. Lighting should be moderate; they do not require intense lighting and actually prefer some shaded areas. A standard aquarium light on a 10- to 12-hour cycle works well.

Filtration should handle the bioload without creating strong currents; a gentle hang-on-back or sponge filter is ideal. African Red Eyes are not strong swimmers and can become exhausted in high-flow tanks. Water changes of 25 to 30 percent weekly keep nitrate levels down and maintain the water clarity they prefer.

Water Conditions and Temperature

African Red Eye Tetras tolerate a fairly broad range of water parameters, which is one reason they are recommended for beginners. Ideal temperature is 72 to 82 degrees Fahrenheit; they can survive outside this range briefly but perform best and show better coloring within it. pH should be slightly acidic to neutral, between 6.0 and 7.0, though they adapt to neutral water without issue.

Water hardness (GH) between 4 and 8 dGH is comfortable for them. They are not as sensitive to hardness as some tetras, so tap water in most regions works fine. The key is consistency—sudden swings in temperature or pH stress them more than a stable suboptimal condition. Use a reliable heater to maintain temperature, especially in cooler climates, and perform regular water tests to track ammonia, nitrite, and nitrate levels.

Feeding and Diet

African Red Eye Tetras are omnivorous and eat a mix of plant and animal matter in the wild. In captivity, a base diet of high-quality flake food or small pellets keeps them healthy, but their red eye coloring intensifies when they receive regular live or frozen foods. Offer brine shrimp, daphnia, or bloodworms two to three times per week. Blanched vegetables like zucchini or spinach can be offered occasionally, though most will ignore plant matter in favor of protein.

Feed small amounts once or twice daily—only what the fish can consume in two to three minutes. Overfeeding fouls the water and leads to bloating or constipation. Young fish and breeding groups benefit from more frequent small meals. Vary the diet to keep the fish interested and to ensure they receive a full spectrum of nutrients.

Compatible Tankmates and Behavior

African Red Eye Tetras are peaceful and do well with other small, non-aggressive fish. Good companions include other tetras, rasboras, corydoras catfish, and small peaceful plecos. They can coexist with dwarf gouramis, though avoid larger or more aggressive cichlids, which may chase or eat them. Shrimp and snails are generally safe, though hungry tetras may occasionally nip at shrimp antennae.

Within their own school, African Red Eyes establish a loose hierarchy but rarely injure one another. They may chase or nip at each other during feeding or when establishing order, but this is normal schooling behavior and not a sign of aggression. If you observe one fish being constantly chased and hiding, the group may be too small or the tank too cramped; adding more plants or increasing group size usually resolves the issue.

Breeding in the Home Aquarium

Breeding African Red Eye Tetras is possible but requires patience and a separate breeding tank. Condition the breeding pair with frequent live foods for two to three weeks until the female appears noticeably rounder. Set up a 10-gallon breeding tank with fine-leaved plants (like Java moss) or a spawning mop, very gentle filtration, and slightly warmer water around 78 to 80 degrees Fahrenheit.

Introduce the pair in the evening. Spawning usually occurs early the next morning; the female will scatter eggs among the plants while the male fertilizes them. Remove the parents immediately after spawning, as they will eat the eggs. The eggs hatch in 24 to 36 hours, and fry become free-swimming three to four days later. Feed infusoria or liquid fry food for the first week, then gradually introduce newly hatched brine shrimp as they grow. Fry grow slowly and are vulnerable to larger fish, so keep them isolated until they reach about half an inch in length.

Common Health Issues and Prevention

African Red Eye Tetras are hardy but can fall ill if water conditions deteriorate or stress builds. The most common problems are fin rot (caused by poor water quality or nipping), ich (a parasitic infection that appears as white spots), and bloating (usually from overfeeding or constipation).

Prevent these by maintaining consistent water parameters, performing regular water changes, and feeding appropriately. If ich appears, raise the temperature gradually to 86 degrees Fahrenheit and treat with an ich medication according to the product label. For fin rot, perform a large water change and improve filtration; antibiotics are rarely needed if water quality improves. Bloating usually resolves with a day or two of fasting followed by smaller, more frequent meals.

Quarantine any new fish for two to three weeks before adding them to the main tank to prevent introducing disease. Watch for signs of stress—constant hiding, loss of appetite, or faded coloring—and investigate water parameters or tankmate compatibility if these appear.

Frequently Asked Questions

Can African Red Eye Tetras live in a 10-gallon tank?

A 10-gallon tank is too small for a proper school of African Red Eyes. The minimum is a 20-gallon long tank for six to eight fish. A 10-gallon tank can work as a breeding or grow-out tank for fry, but adult fish need more space to school and establish territories without constant stress.

Do African Red Eye Tetras need a heater?

If your room temperature stays between 72 and 82 degrees Fahrenheit year-round, a heater may not be necessary. Most homes require one, especially in winter or in cooler climates. A reliable heater prevents temperature swings that stress the fish and trigger illness.

Why are my African Red Eyes losing their red coloring?

Faded coloring usually signals poor diet, stress, or declining water quality. Increase live or frozen food offerings, check water parameters for ammonia or nitrite spikes, and ensure the group is large enough (at least six fish). Coloring typically returns within two to three weeks of improved conditions.

How long do African Red Eye Tetras live?

With proper care, African Red Eye Tetras typically live four to six years in captivity. Some individuals reach seven years in very stable, well-maintained tanks. Lifespan depends heavily on water quality, diet, and the absence of stress or disease.

Can I keep African Red Eye Tetras with bettas?

It depends on the individual betta. Some bettas ignore small tetras, while others chase and bite them relentlessly. If you want to try it, introduce the tetras first and watch closely for the first week. If the betta attacks, move it to a separate tank immediately.