Care guide · Freshwater · fish

Foersch’s notho

Nothobranchius foerschi

Male Nothobranchius foerschi. Photo: Jokuyken15, CC BY 4.0 (resized proportionally). Photo: Jokuyken15 / Wikimedia Commons · Source · CC BY 4.0Proportional resize only; no crop or colour edit. Attribution and CC BY 4.0 terms retained.

Foersch’s notho (Nothobranchius foerschi) is a colourful annual killifish from eastern Tanzania. Its range appears restricted to the Ruvu River catchment and delta. Males show a blue-green body with red scale margins and striking fins; females are smaller and less vivid. The species inhabits temporary pools and swamps that may disappear during the dry season. Its eggs bridge that period in the substrate. This makes breeding fascinating, but it also calls for preparation and a plan for the short adult phase. It is not a routine community fish. The global assessment is Vulnerable (VU, 2018); favour traceable captive-bred stock and leave wild fish and their habitats undisturbed.

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At a glance

Temperature: 20–24 °C
pH: 6.5–7.5
GH: 10–25 °dGH
Aquarium length: At least 45 cm
Minimum aquarium volume: At least 41 L
Adult size: Up to 5.5 cm
Group size: At least 2 individuals
Temperament: Predator

About this species

GBIF and specialist fish sources accept Nothobranchius foerschi Wildekamp & Berkenkamp, 1979, in Nothobranchiidae. It was described from Soga in eastern Tanzania. Seriously Fish reports that all confirmed records are from the Ruvu catchment and delta, between Soga and the coast near Bagamoyo. An old record from the Rufiji area is uncertain and is not treated as equivalent evidence. Seriously Fish gives males at about 55 mm standard length and females around 40 mm. These are standard lengths, not total lengths. An aquarium strain may appear yellower than the wild form; this colour difference does not make it a separate species. Do not confuse it with Desmopuntius foerschi, a Bornean barb sharing the same species epithet.

Natural habitat

The species inhabits temporary water-filled depressions, pools and swamps on lowland floodplains in eastern Tanzania. These sites fill in the rainy season; during the dry season, water levels fall and the sites may dry for months. Fish deposit eggs in the substrate; embryonic development can include resting phases before rain and water return. Near Bagamoyo fish have been collected from flat, grassy floodplains alongside other Nothobranchius species, while different congeners occur around Soga. Margins are usually heavily overgrown with terrestrial vegetation. This explains the value of cover, but it does not mean a home aquarium should be allowed to dry. Keep captive water stable and use checked parameters. FishBase lists natural-water values of 22–26°C and pH 6.5–7.5; these are field data, not a reason to exceed specialist aquarium guidance.

Aquarium and layout

Seriously Fish recommends a base of at least 45 × 30 cm and gives an approximate volume of 41 litres; actual capacity depends on water height. Even a pair should normally have that footprint, except when temporarily isolated for spawning. Use a secure lid because killifish can jump. Dense plants, floating cover, wood or other safe decor can break sightlines. Keep flow controlled, provide biological filtration and maintain the aquarium regularly. The specialist source considers the species unsuitable for a standard community tank. Plan adult housing, any separate breeding setup and juvenile rearing before acquiring fish. A small temporary spawning container does not replace a stable permanent aquarium.

Water conditions

For aquarium care, Seriously Fish gives 20–24°C, pH 6.5–7.5 and GH 10–25 °dGH. FishBase reports natural water values of 22–26°C and pH 6.5–7.5. The temperature sources overlap at 22–24°C. The wider FishBase range describes field water; it is not aquarium advice to heat the tank to 26°C. Keep a stable temperature within the specialist aquarium range. Test your source water and acclimate gradually; do not correct pH rapidly. Avoid swings, waste build-up and unnecessary additives. The hardness range is a specialist aquarium recommendation, not a measurement covering every collection site. Do not add salt, peat or buffers without a clear reason and monitoring plan.

Behaviour and group size

Seriously Fish describes the species as unsuitable for a community aquarium and gives pair housing as the social reference. This is a starting point, not a guarantee that every male-female pair will remain calm. Watch for chasing, damaged fins and interrupted feeding. Provide cover and escape routes. Small juveniles and small animals may be at risk from this micropredator. Do not mix population lines without provenance; retain any breeder locality codes. Since generally safe tankmates cannot be confirmed responsibly, this guide does not recommend other fish as suitable combinations. A species tank makes behaviour and feeding easier to monitor.

Feeding

Foersch’s notho is a micropredator. Seriously Fish lists small live or frozen prey such as Daphnia, Artemia and finely chopped bloodworm as the dietary basis. Offer small portions that are eaten promptly and rotate suitable prey. Dry food is not established as a complete staple; use it only as a supplement if you observe the fish eating it. Remove leftovers promptly to protect water quality. Newly hatched fry need suitably small live food. Exact first foods and timing depend on fry size and developmental stage; follow an experienced killifish breeder and confirm each fry is feeding. The central catalogue currently has no verified suitable staple food product for this micropredator, so no unsuitable product is linked.

Breeding

As an annual killifish, Nothobranchius foerschi lays eggs in substrate that can withstand a dry phase. The American Killifish Association describes seasonal pools and embryonic resting phases for the genus; the BKA gives about 12–16 weeks at 23–24°C as a guide for N. foerschi. Duration can vary by line and moisture, so this is not a fixed guarantee. Seriously Fish says peat is not required for routine maintenance, although peat moss is often used as a spawning medium. For deliberate breeding, label the medium, species, population code and date; keep it moist rather than wet and inspect eggs before re-wetting. Arrange appropriate first foods and enough rearing space in advance. Breed only when offspring can be responsibly housed and placed.

Sources & review

This care guide draws on several specialist sources and was last checked on 17 October 2026.

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