Killifish Egg Storage Guide — Diapause Management for Annual Species

Annual killifish are among the most extraordinary fish in the hobby — not because of their size or temperament, but because of a biological adaptation that defies the usual rules of aquarium keeping. Their eggs can survive completely desiccated in a bag of damp peat moss for months, even years, waiting patiently for conditions that signal it is safe to hatch. Mastering egg storage and diapause management is the gateway to keeping these remarkable fish successfully.

What Are Annual Killifish?

Annual killifish are species native to ephemeral pools in sub-Saharan Africa and South America — bodies of water that fill during the rainy season and evaporate completely during the dry months. Because adults cannot survive the dry season, the entire population dies, leaving only buried eggs to carry the lineage forward. These eggs enter a state of suspended development called diapause, a form of biological dormancy that allows the embryo to pause mid-development until environmental cues signal that water has returned.

Popular annual species include Nothobranchius (African annuals such as N. rachovii, N. korthausae, and N. furzeri) and New World annuals like Austrolebias and Simpsonichthys. Each genus has slightly different diapause requirements, but the core principles of collection, storage, and hatching remain consistent.

Collecting Eggs from Spawning Pairs

To collect eggs, prepare a shallow container — a plastic food tub or breeding box works well — filled with 2–3 cm of peat moss that has been boiled, cooled, and mixed with a small amount of tank water to reach a moist but not saturated consistency. Introduce a conditioned pair into the container and allow them to spawn. Annual killifish instinctively dive into substrate to deposit eggs, so the peat medium closely mimics their natural environment.

Leave the pair in for one to two weeks, then remove the adults. Pour the peat through a fine net to separate out any excess water, then gently press the peat between your palms to squeeze out moisture. You are aiming for a consistency sometimes described as "damp potting soil" — the peat should hold together when squeezed but release no drips. Too wet encourages fungal growth and premature hatching; too dry will kill the embryos.

Diapause Storage Conditions

Place the pressed peat into a resealable plastic bag or small airtight container. Label clearly with the species name, collection date, and the expected minimum diapause period. Store at 22–26°C in a dark location — a drawer or cupboard works perfectly. Avoid refrigerators, which are too cold for most species, and avoid locations with large temperature swings.