What the African Red-Eyed Tetra Is and Why It Matters

The African red-eyed tetra (Arnoldichthys spilopterus) is a small, schooling fish native to West Africa, recognizable by its bright red eye and metallic body that shifts between silver and gold depending on light. It grows to about 2 inches long and lives 4 to 5 years in captivity. Unlike many tetras sold in the aquarium trade, this species is less common than neon or cardinal tetras but offers the same active, peaceful behavior in a community tank.

The fish gets its name from the distinctive red coloring around its eye, which becomes more vivid when the fish is healthy and well-fed. In the wild, it inhabits slow-moving streams and tributaries in Nigeria and Cameroon, living in groups of dozens or more. That schooling instinct remains strong in captivity, and the fish shows its best colors and behavior only when kept with others of its kind.

Key Takeaways

  • African red-eyed tetras must be kept in groups of at least 6 to 8 fish, or they become stressed and lose color.
  • A 20-gallon long tank is the practical minimum for a school, with gentle filtration and plants to mimic their natural habitat.
  • Water temperature should stay between 72 and 82 degrees Fahrenheit, with a pH between 6.0 and 7.0.
  • They eat small live foods like micro worms and daphnia in addition to quality flake food, and breeding is possible in home aquariums with the right setup.

Tank Size and Setup for a School

A single African red-eyed tetra in a small tank will not thrive. The minimum practical setup is a 20-gallon long tank for a school of 6 to 8 fish. Long tanks are better than tall ones because they provide more horizontal swimming space, which these active fish need. If you want to keep 12 or more, a 40-gallon breeder tank or larger gives them room to move without crowding.

Filtration should be gentle—these fish come from slow-moving water and dislike strong current. A sponge filter or a hang-on-back filter set to low flow works better than a powerful canister. Add live plants like Java fern, Anubias, or stem plants such as ludwigia. Plants provide cover, reduce stress, and help keep the water stable. A dark substrate (sand or fine gravel) and driftwood make the tank feel more like their natural environment and bring out the fish's colors.

Lighting should be moderate—8 to 10 hours per day is enough. Avoid intense lighting unless you are growing demanding plants; these fish prefer dimmer conditions. A small air stone or gentle water movement helps, but avoid powerheads or strong jets.

Water Conditions and Temperature

African red-eyed tetras are not difficult about water chemistry, but they do best in slightly acidic to neutral water. Keep the pH between 6.0 and 7.0, and aim for a temperature between 72 and 82 degrees Fahrenheit. Most home aquariums sit comfortably in this range without a heater during warm months, but a 50 to 75-watt heater is worth having for winter or cooler climates.

Water hardness should be soft to moderately soft—between 4 and 8 dGH (degrees of general hardness). If your tap water is very hard, mixing in distilled water or using reverse osmosis water can help. Weekly water changes of 25 to 30 percent keep nitrate levels down and maintain stable conditions. Test the water with a basic kit when you first set up the tank, then monthly after that.

Feeding and Diet

In the wild, African red-eyed tetras eat small insects, crustaceans, and plant matter. In captivity, they thrive on a mix of foods. High-quality flake food or micro pellets should be the base, but they show their best colors and health when fed live or frozen foods several times a week. Micro worms, daphnia, and newly hatched brine shrimp are ideal because they are small enough for the fish's tiny mouth and trigger natural feeding behavior.

Feed small amounts twice a day—only what the fish can eat in 2 to 3 minutes. Overfeeding fouls the water and causes bloating. If you are breeding them, live food becomes even more important; fry will not eat flake food at first and need infusoria or micro worms to survive.

Temperament and Tank Mates

African red-eyed tetras are peaceful and do not nip fins, making them safe in community tanks with other small, calm fish. Good tank mates include other tetras, rasboras, small corydoras catfish, and peaceful dwarf cichlids like ram cichlids. Avoid large or aggressive fish, and do not mix them with fin-nippers like tiger barbs or serpae tetras.

Within their own school, they are gentle. Males may chase each other during feeding or spawning, but this is normal and not harmful. Keeping them in groups of 8 or more spreads any aggression so thinly that no single fish is targeted. A school of 12 or more is ideal if space allows.

Breeding in the Home Aquarium

African red-eyed tetras breed readily in captivity if conditions are right. Set up a separate breeding tank of at least 10 gallons with fine-leaved plants (such as Java moss or spawning mop) where eggs can stick. Fill it with water from your main tank to match temperature and chemistry, then add a pair or small group of well-fed fish in the evening.

Spawning usually happens at dawn. The female scatters eggs among the plants while the male fertilizes them. Remove the adults immediately after spawning, because they will eat the eggs. The eggs hatch in 24 to 36 hours, and fry become free-swimming 3 to 4 days later. Feed them infusoria or liquid fry food for the first week, then micro worms and very small live foods. After 2 to 3 weeks, they can eat crushed flake food.

Raising fry to sellable size takes 8 to 12 weeks. Do frequent small water changes (10 to 15 percent every other day) to keep the water clean without shocking the young fish. Once they reach about half an inch, they can move to a larger grow-out tank or back to the main aquarium if it is large enough.

Common Health Issues and Prevention

African red-eyed tetras are hardy but can develop ich (white spot disease) if stressed or exposed to temperature swings. Keep the tank stable, maintain good water quality, and avoid sudden changes. If ich appears, raise the temperature to 82 to 84 degrees and treat with salt or a commercial ich remedy according to the product instructions.

Fin rot and fungal infections occur in poor water conditions. Regular water changes and gentle filtration prevent these. If a fish shows torn fins or white fuzz, do a 50 percent water change, check your filter, and treat with an antifungal if the problem spreads. Stressed or overcrowded fish are more prone to disease, so maintaining a proper school size and tank volume is the best prevention.

Where to Source African Red-Eyed Tetras

These fish are less common than neon or cardinal tetras but are available from specialty aquarium shops and online retailers that ship live fish. Prices typically range from $3 to $6 per fish, depending on size and source. When ordering online, choose a shipper with good reviews and insulated packaging, and acclimate the fish slowly to your tank water using the drip method over 30 to 45 minutes.

Local aquarium clubs sometimes have members who breed them, and buying from a hobbyist breeder often means healthier, locally adapted fish. Ask at your local shop if they know of any breeders in your area.

Frequently Asked Questions

Can I keep African red-eyed tetras with shrimp?

Yes, they are small enough that they will not hunt adult shrimp, though they may eat shrimp fry if given the chance. Amano shrimp and larger species like ghost shrimp are safe. Keep plenty of plants for the shrimp to hide in.

Do they need a heater?

If your room stays between 72 and 82 degrees year-round, no. If temperatures drop below 70 in winter, a small heater prevents stress and disease. A 50-watt heater is enough for a 20-gallon tank.

Why are my fish losing color?

Color fades when fish are stressed, underfed, or kept alone or in small groups. Check water quality, increase school size to at least 8 fish, and offer live or frozen foods several times a week. Color usually returns within 2 to 3 weeks.

How long do they live?

African red-eyed tetras typically live 4 to 5 years in a well-maintained tank. Some live longer if water conditions are stable and diet is good.

Are they hard to breed?

No. They spawn readily if given plants, good food, and stable water. The challenge is raising the fry, which need infusoria or micro worms for the first few weeks. Once fry are large enough to eat small foods, survival rates improve.