Care guide · Freshwater · fish
African red-eyed tetra
Arnoldichthys spilopterus
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Arnoldichthys spilopterus, the African red-eyed tetra or Niger tetra, is a large and active shoaling fish from Nigeria. It is the only described species in the genus Arnoldichthys. Older aquarium sources place it in Alestidae, while current resources such as FishBase use Lepidarchidae. Historical literature may use Petersius spilopterus. Its red iris and large scales are distinctive, but confirm the scientific name when buying. This is not a small tetra for a compact aquarium. Its restricted range and current conservation concern also make provenance and responsible sourcing especially relevant.
Plan your aquarium →At a glance
- Temperature
- 24–27 °C
- pH
- 6.0–7.5
- GH
- 1–15 °dGH
- Aquarium length
- At least 120 cm
- Minimum aquarium volume
- At least 108 L
- Adult size
- At least 9.6 cm
- Group size
- At least 10 individuals
- Temperament
- Peaceful
About this species
Seriously Fish reports 100 mm standard length; FishBase gives 9.6 cm standard length. Standard length is measured to the tail base and excludes the caudal fin. Adults are therefore substantial for a fish sold as a tetra. The aquarium profile notes that males are slimmer and have dark stripes in the anal fin, while females are fuller-bodied. Consider adult size when planning food, tankmates and swimming room.Natural habitat
The species is endemic to Nigeria and known from the lower Niger and Ogun rivers. Seriously Fish describes localities within an area experiencing ongoing deforestation and pollution, and says the fish is known from fewer than ten sites. Prefer demonstrably captive-bred stock where possible and ask about provenance. Habitat information is limited; sources mention streams and rivers. An exact biotope or local water recipe cannot be responsibly supplied from the available evidence.Aquarium and layout
Seriously Fish recommends a tank base of at least 120 by 30 cm, about 108 litres, and says this should be the smallest size considered. Keep at least ten fish for natural shoaling behaviour. The species is very active and needs open swimming room; also provide sheltered areas to reduce startle. A secure lid is prudent for active fish. Volume alone does not show whether the required length and clear swimming area are present.Water conditions
The aquarium profile lists 24–27°C, pH 6.0–7.5 and GH 1–15 dGH. FishBase gives broader ecological references of 23–28°C and pH 6–8. This difference does not mean the fish tolerates rapid changes. Use the specialist aquarium range as a practical guide, keep water quality stable and acclimate gradually. Measure carefully and base adjustments on the actual conditions in which the fish were held.Behaviour and group size
The African red-eyed tetra is peaceful but very active. Shy or slow-moving tankmates may be disadvantaged by its activity and food competition; long-finned species require extra care. Choose robust fish of comparable size and make sure the shoal has enough room. Consider group size, behaviour, adult dimensions and feeding zone. Matching temperature or pH alone does not prove a safe combination.Feeding
The species accepts a range of foods. Small live or frozen foods such as Artemia, Daphnia and mosquito larvae can support a varied diet alongside quality flakes or granules sized for its mouth. Feed portions the shoal can consume promptly and ensure less dominant fish get access. Alternate dry and animal-based foods and remove leftovers. The available evidence does not justify an exclusive diet or a specific brand recommendation.Breeding
The specialist source notes conflicting breeding reports but describes the fish as an egg scatterer without parental care. A separate tank, conditioning with live or frozen foods and a mesh floor to protect eggs are reported options, not a guaranteed recipe. FishBase cites reports of up to one thousand eggs and hatching after about 30–34 hours, but results vary. Newly hatched fry first need fine food. Do not promise egg counts or breeding success.Sources & review
This care guide draws on several specialist sources and was last checked on .
View the sources
- Seriously Fish — Arnoldichthys spilopterus — aquarium size, water, group, diet and breeding
- FishBase — Arnoldichthys spilopterus — current family, distribution, size and IUCN assessment
- California Academy of Sciences — Eschmeyer’s Catalog of Fishes — valid name and nomenclature
- Royal Museum for Central Africa — CLOFFA — curated West African freshwater fish taxon record