Care guide · Freshwater · fish

Yellow-tailed Congo tetra

Alestopetersius caudalis

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Alestopetersius caudalis, the yellow-tailed Congo tetra, is an African shoaling fish in the family Alestidae. It is also sold as the yellow-finned, yellowtail or blue Congo tetra. Do not confuse it with the larger, better-known Congo tetra Phenacogrammus interruptus. Older literature uses synonyms such as Petersius caudalis; this guide uses the currently accepted name. The species comes from the lower Congo region and can be kept in a spacious community aquarium when group size, swimming room and tankmates are chosen carefully. A long aquarium with room for the active shoal helps reduce startle responses and competition between fish.

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At a glance

Temperature: 22–26 °C
pH: 5.0–7.5
GH: 2–15 °dGH
Aquarium length: At least 120 cm
Minimum aquarium volume: At least 108 L
Adult size: At least 6 cm
Group size: At least 8 individuals
Temperament: Peaceful

About this species

Seriously Fish reports about 60 mm standard length. FishBase lists around 6.2 cm total length. The difference reflects measurement convention: standard length ends at the tail base, while total length includes the caudal fin. Adult males become more colourful and may grow larger; extended fin rays are characteristic. Rival males may display and chase. Space and visual breaks help prevent this behaviour from causing injuries in a cramped aquarium.

Natural habitat

The species was described from the lower Congo region of the Democratic Republic of the Congo, with records upriver to the Irebu channel and the Lake Tumba area. Specialist information notes that little has been published about its exact natural habitat and biology. It would therefore be unwarranted to invent a highly specific biotope from sparse evidence. Open swimming room, suitable current and sheltered areas fit the available aquarium observations.

Aquarium and layout

Seriously Fish recommends a tank base of at least 120 by 30 cm, about 108 litres. This is a footprint and swimming-space guideline, not a universal guarantee for every stocking plan. Keep eight to ten or more fish where possible and provide room for an active shoal. Rival males may chase one another; in cramped conditions, scale loss and injuries can occur. Combine open water with calm refuges and monitor the fish regularly.

Water conditions

The specialist care profile lists 22–26°C, pH 5.0–7.5 and GH 2–15 dGH. FishBase gives narrower reference values for natural conditions. Treat the aquarium figures as boundaries from one source, not as a reason to pursue large changes. Keep water quality stable, test carefully and acclimate new fish gradually. Ask the breeder or supplier about previous conditions where possible.

Behaviour and group size

The yellow-tailed Congo tetra is lively, sometimes skittish and generally peaceful. Choose tankmates of compatible size and activity that will not continually take its food. It can share a spacious aquarium with calm fish from other swimming zones. Account for its shoaling needs and male display behaviour. Overlapping water values alone do not prove compatibility; behaviour, adult size, group dynamics and space matter just as much.

Feeding

Alestopetersius caudalis is an omnivorous forager. Its presumed wild diet includes small insects, crustaceans and fallen fruit. Offer quality dry food in an appropriate size as a staple, supplemented with small portions of live or frozen foods such as Artemia, Daphnia and bloodworm. Some plant or algal content in the dry foods is useful. Observe all fish feeding and avoid overfeeding.

Breeding

Regular aquarium breeding appears uncommon according to the specialist profile, and details are limited. The species is described as an egg scatterer without parental care. A separate tank and egg trap are mentioned as a possible approach, but this is not a guaranteed protocol. Remove eggs if found to reduce predation by adults. Newly hatched fry first need microscopic food, followed later by suitably small foods. Success remains uncertain.

Sources & review

This care guide draws on several specialist sources and was last checked on 16 October 2026.

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