Nothobranchius foerschi

Nothobranchius foerschi is a small annual killifish from coastal Tanzania. Males are striking, with green-blue bodies, red-reticulated scales, and a bright red tail. At up to 5 cm, it is a true nano fish, but it has plenty of personality and a short, fast life: most live 6-9 months.

Origin and natural habitat

This species inhabits seasonal pools in East Africa, specifically coastal Tanzania. These waters fill during the rains and dry out later in the year. N. foerschi has adapted to this cycle by laying eggs that pause development in dry peat-like substrate, then resume when water returns. That life history explains its short adult lifespan in the aquarium.

Aquarium setup and water conditions

Give this fish calm, shallow-feeling water with good cover. A planted setup with floating plants, leaf litter, or fine-leaved stems helps them feel secure and shows off the males' colors. Keep flow gentle.

• Minimum tank: 10 US gallons
• Temperature: 22-26 C
• pH: 6.5-7.5
• Water: freshwater; keep clean and stable with regular small changes

Diet and feeding

A carnivore by nature, N. foerschi does best on live and frozen foods. Offer insect larvae (such as mosquito larvae), daphnia, and brine shrimp. Many individuals will also accept high-quality flakes once settled, but keep live or frozen foods as the core of the diet.

• Feed small portions 1-2 times daily
• Vary offerings to keep condition and color up
• Remove uneaten food to protect water quality

Behaviour and tankmates

Classed as semi-aggressive, males display and spar, and can be nippy. They are not schooling fish. The simplest approach is a species-only tank with one male and females. If you try a community, choose quick, robust companions and avoid slow or long-finned fish that invite nipping. Provide plenty of cover to break lines of sight.

Breeding

Captive breeding is well documented for this annual killifish. They are substrate spawners that bury eggs. The usual method is to place a container of rinsed peat moss in the tank as a spawning site. Adults dive into it to lay eggs.

• After spawning, remove the peat with eggs and keep it moist (not waterlogged).
• Store the moist peat sealed for a dry period; the embryos pause development during this time.
• After the dry period, re-wet the peat with conditioned water. Fry typically hatch shortly after wetting.
• Start fry on very small live foods such as newly hatched brine shrimp; keep water clean with gentle changes.

Common problems and how to avoid them

• Jumping: Always use a tight lid with no gaps.
• Male aggression: Limit to one male per 10-gallon setup and provide dense cover.
• Poor condition on dry foods alone: Base the diet on live or frozen items; use flakes only as a supplement if accepted.
• Water quality swings: Keep up with small, regular water changes and avoid overfeeding in a nano tank.