Rachovi Killifish

The rachovi killifish (Nothobranchius rachovii), also known as the bluefin notho, is a small annual killifish native to coastal floodplain pools near Beira, Mozambique. It belongs to the family Nothobranchiidae and is one of the most iconic Nothobranchius species due to the vivid, multicolored patterning of breeding males. Like other annual killifish, it lives in temporary pools that form during the rainy season and dry out completely later in the year, restricting the species to a life cycle measured in months rather than years. It is widely bred in the aquarium hobby and frequently used as a reference species for Nothobranchius taxonomy.

Rachovi killifish are small, reaching about 5-6 cm.

• Body: slender and slightly compressed, typical of surface-dwelling annual killifish
• Male coloration: iridescent turquoise-blue body overlaid with a fine red net-like or barred pattern
• Tail: distinctive tricolor pattern with a red center band bordered by blue and yellow-edged margins
• Female coloration: plain gray-olive with rounded, unpatterned fins

The banded, tricolor tail pattern helps separate it from similar species such as the redtail notho, which shows a solid red tail rather than distinct color bands.

This species is restricted to temporary floodplain pools and marshy depressions near Beira on the coast of Mozambique, in low-lying savanna terrain subject to seasonal flooding. Pools form during the rainy season and typically dry out completely during the dry months, so the species has no permanent aquatic range. Water in these habitats is shallow, warm, and often turbid, with a soft muddy substrate suited to egg burial. As with other Nothobranchius, populations persist through the dry season only as diapausing eggs in the dried mud.

Rachovi killifish grow and mature quickly, reflecting the short lifespan of their temporary pool habitat. They are substrate spawners, with pairs diving into soft mud to bury eggs that can withstand months of desiccation through diapause. Adults feed actively near the surface and midwater on mosquito larvae, small crustaceans, and other invertebrates. Males display vividly and compete for spawning access to females, establishing loose, temporary territories over favored substrate. When the pool dries completely, the adult population dies off entirely, and the next generation emerges only once rains refill the depression and trigger synchronized hatching.