Korthaus' Nothobranchius (Nothobranchius korthausae) Breeding Guide

Breeding the annual killifish Nothobranchius korthausae: peat spawning, drying eggs through diapause, and wetting damp peat to hatch fry.

Overview

Nothobranchius korthausae is an annual killifish endemic to Mafia Island, Tanzania, where it lives in temporary pools, swamps, ditches and small streams that dry up each year. FishBase records it at up to about 5 cm, in soft acidic water (pH 5.8-6.4) at 23-26 °C. Adults die when their pools evaporate, but their eggs survive buried in the substrate, a classic annual lifecycle.

Sexing

Sexing is straightforward in Nothobranchius. Males are larger and brightly coloured with red and yellow patterns, while females are smaller and a plain silvery-brown. A typical breeding group is a single male with several females.

Conditioning

These fish are carnivores that should be conditioned heavily on small live and frozen foods such as daphnia, bloodworm and brine shrimp. Well-fed females ripen continuously and spawn daily over peat, so steady feeding directly drives egg output.

Breeding Setup

Add a male and females to a small tank with a container holding 2 to 3 inches of peat or coir as a spawning substrate. The fish dive into the soft peat to bury their eggs. A gentle sponge or box filter and dim conditions keep the spawners calm.

Spawning Behavior & Trigger

Pairs push down into the peat and release eggs into the medium, repeating throughout the day. The egg-laden peat is collected, gently squeezed to remove excess water until it has a damp, crumbly consistency, and then sealed in a plastic bag or jar for incubation.

Egg Diapause & Hatching

The damp peat is stored at room temperature, where embryonic development takes about two to three months; FishBase gives an incubation of one to three months. Annual killifish eggs can pause development in diapause until conditions are right. At the end of the storage period the peat is tipped into a container and flooded with soft, cool water, which triggers hatching as the embryos detect submersion. Fry are large enough to take baby brine shrimp and microworms immediately.

Common Challenges

Storing the peat too wet or too dry, or at the wrong temperature, disrupts diapause and can kill eggs or produce weak fry. Keeping the peat damp rather than soaking, and re-drying and re-wetting a second time, often recovers eggs that did not hatch on the first wetting.