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The Nothobranchius guentheri, also called Red Tail, is an annual killifish native to seasonal wetlands in East Africa. This small fish is fascinating because of its rapid life cycle, vivid colors, and ability to produce eggs that survive the temporary drying of its habitat. Males generally display a bluish body marked with red and a brightly colored tail, while females are more subdued. In an aquarium, this species needs clean water, a stable temperature, and a suitable spawning medium for successful breeding.

General species description

Nothobranchius guentheri is a small annual fish from the family Nothobranchiidae, adapted to temporary pools that fill during the rainy season and later dry out. Its development is rapid, and its reproductive cycle is closely tied to this seasonal pattern. Males are highly colorful and defend small territories near the bottom, while females are more discreet. In an aquarium, it is best kept in a group with several females per male to reduce the pressure caused by courtship. Spawning takes place in a soft substrate, such as peat or a specialized spawning medium. This species is best suited to aquarists interested in killifish and annual breeding cycles.

Geographical origin and biotope (reference countries: Tanzania, Kenya)

Nothobranchius guentheri comes from East Africa, especially Tanzania and Kenya, where it inhabits floodable depressions and temporary pools associated with coastal plains. The water is generally still, shallow, and sometimes darkened by organic matter. These habitats can experience major seasonal changes in temperature, water level, and oxygen concentration. Such conditions explain the production of resistant eggs that can remain in damp soil during the dry period. In an aquarium, soft to moderately mineralized water that is slightly acidic to neutral is more suitable than strongly alkaline conditions. Floating plants or fine-leaved plants help create shelter and reduce intense lighting.

Precise location and local name

The species is particularly associated with Zanzibar and coastal areas of Tanzania, as well as some coastal regions of Kenya. It is found in temporary pools, natural ditches, and small depressions filled by seasonal rainfall rather than in a permanent river. The aquarium and trade name Red Tail refers to the red coloration of the male’s caudal fin. Populations may show differences in color depending on their geographic origin, so separate strains should be maintained separately to prevent mixing different localities.

Appearance and physical characteristics

The adult male reaches about 7 cm and has an elongated, laterally compressed body with relatively well-developed fins. Its basic coloration ranges from metallic blue to blue-green, with red spots and markings across the body and fins. The tail is often orange-red and especially noticeable, explaining the name Red Tail. Females are usually smaller or slimmer in appearance and typically show beige-gray to brownish coloration, with less contrasting fins. The sexual dimorphism becomes obvious as soon as males begin to develop their adult colors. Moderate lighting and a dark background enhance the fish’s colors without making it overly nervous.

General diet

In nature, Nothobranchius guentheri mainly feeds on small aquatic and terrestrial prey, including insect larvae, small crustaceans, and other suitably sized organisms. In aquariums, it readily accepts frozen foods such as brine shrimp, mosquito larvae, and daphnia. High-quality dry foods can also be offered, but they should supplement rather than replace protein-rich prey. Young fish benefit from frequent meals made of finely sized food. Small portions should be offered once or twice daily, with leftovers removed. A varied diet supports stronger coloration, steady growth, and good reproductive condition.

Essential data

• Origin river: Habitat made up of temporary pools; no associated permanent river is retained.
• Local name used: Red Tail, an English aquarium name.
• Origin of the scientific name: The specific name honors Albert Günther; the genus refers to gills.
• Etymology of the full name: Nothobranchius comes from the Greek nothos, false, and branchion, gill; guentheri honors Albert Günther.
• Common/vernacular names: Red Tail, Günther’s annual killifish.
• Family: Nothobranchiidae
• Subfamily: Nothobranchiinae
• Name pronunciation: no-tho-BRAN-kee-us - GUEN-thur-eye
• Discovery: Described by Georg Johann Pfeffer in 1893.
• Maximum adult size: About 7 cm.
• Water temperature and pH: About 22 to 28 °C; pH 6.0 to 7.5.
• Stream appearance and surrounding vegetation: Calm, shallow seasonal pools bordered by grasses, terrestrial plants, and sometimes floating vegetation.
• Typical tankmates: Best kept in a species aquarium; temporary pools do not represent a permanent community habitat.
• Temperament and behavior: Active; males display, defend small territories, and may persistently court females.
• Water depth: Shallow, generally limited to seasonal pools and depressions.
• Bottom structure and flow: Muddy or sandy bottom rich in organic matter; stagnant water or almost no current.

In your aquarium

Success with Nothobranchius guentheri depends on clean water, a stable temperature, and a covered aquarium because killifish can jump. Provide subdued lighting, floating plants, and an easily removable spawning medium. For breeding, periodically remove the medium containing the eggs and follow an incubation schedule suited to the strain. A diet based on frozen or live foods supports coloration and vitality. Species-only maintenance also makes it easier to manage courtship behavior and protect females from repeated chasing.