Bluefin Notho

Nothobranchius rachovii is one of the most colorful members of the group known as annual (seasonal) killifish. The males' metallic blue body is woven with red-orange scale edges and vertical lines; the fins are fiery in color and the tip of the tail has a black edge. Females, on the other hand, are plain gray-brown.

The life of annual killifish is built around the drought cycle in nature: the fish hatch in temporary pools that fill in the rainy season, mature in a few weeks, bury their eggs in the mud and die when the pool dries out. The new generation is born from the eggs in the dry mud with the next rains. This is why its lifespan in the aquarium is also short (usually 12–18 months), and the only way to keep it going is to collect and store the eggs regularly.

It lives in shallow, murky pools that fill during the rainy season on the savannas and floodplains of central Mozambique. These waters evaporate and dry out completely within a few months; the temperature varies markedly during the day and over the season.

• Volume: 30–40 liters is enough for one male and two to three females; a species tank is recommended.
• Substrate: A dark substrate or bare bottom; a small container filled with boiled peat for spawning.
• Water: 22–24°C, soft to moderately hard, close to neutral. An air-driven sponge filter is enough; it does not want strong flow.
• Lid: A tight lid is essential; it jumps.
• Maintenance: 30% water change weekly. Because it eats a lot, the water fouls quickly.

Carnivorous, and because it grows fast its appetite is very high. The staple should be live or frozen food: bloodworms, daphnia, mosquito larvae, brine shrimp. Most individuals eat dry food reluctantly. Feed twice a day, no more than is eaten without leftovers.

Males are quarrelsome with each other and chase the females intensely. Because of its short life and special breeding routine, it is best kept in a species tank.

Good companions: females of its own species; males of other annual species in a large aquarium with separate compartments.

Avoid: sharing a tank with other Nothobranchius species (the females are almost impossible to tell apart, and hybridization occurs), fin nippers and large fish, community fish that need warm water.

Two to three females per male is the most balanced setup. If two males are kept together in a small aquarium, the dominant male wears the other down. If there are too few females, the male's attention focuses on a single female and she becomes exhausted.

The pair dives into the peat in the spawning container and buries the eggs one by one. Care steps:

• Collecting: The peat is removed every 1–2 weeks, drained in a fine net and squeezed by hand to remove excess water; it should be damp but not dripping, like soil.
• Storage: It is kept in a zip-lock bag labeled with the species name and date, at 20–24°C, in the dark. The peat must neither dry out completely nor stay wet.
• Duration: usually 3–5 months; shorter in a warm environment. If dark eyes and a golden ring are visible inside the eggs, the embryo is ready.
• Wetting: The peat is placed in soft water a few centimeters deep at 18–20°C. The fry hatch within hours; eggs that do not hatch are dried again with the peat and tried again a few weeks later.

The fry eat newly hatched brine shrimp from the first day, grow very fast and color up in about two months. The water level should be kept low in the first days; otherwise "belly sliders" that cannot fill their swim bladder appear.

• Short life: In individuals past one year of age, fading color, a hunched back and loss of appetite are natural aging.
• Velvet (Oodinium): common in Nothobranchius. Some keepers add about 1 gram of salt per liter of water as a precaution; do this only in a tank where the species is kept alone.
• Stale water and leftover food speed up bacterial problems.

Sexing is very easy. Males have a blue-red pattern and colorful fins; females are plain gray-brown with transparent, colorless fins. Males are slightly larger and have broader fins.