Longfin Killifish Breeding Guide

How to breed Pterolebias longipinnis, an Amazonian annual killifish whose eggs are buried in peat and dry-incubated for several months before wetting.

Overview

Pterolebias longipinnis is a member of the family Rivulidae from the Amazon and Paraguay River basins of South America. It is an annual killifish: it lives in temporary pools that dry out seasonally, and its eggs survive the dry season buried in the substrate. FishBase records it as a bottom spawner with roughly three months of incubation, reaching a maximum total length of about 12 cm.

Sexing

Males of annual killifish are the larger, more colourful sex and carry the long, extended unpaired fins that give this species its flag-like profile. Females are plainer and shorter-finned. A single male with one or two females is a typical breeding group.

Conditioning

This species feeds on worms, crustaceans and insects in nature. Isolating the intended breeders and preconditioning them with live or high-quality frozen foods for about a week before spawning markedly increases success, according to Tropical Fish Hobbyist.

Breeding Setup

Annual Rivulidae are bred over a spawning substrate. Tropical Fish Hobbyist recommends a layer of fertiliser-free peat moss or fibre, boiled for a few minutes to sterilise it and to make it sink. The breeders are added over the peat and the container is covered. FishBase lists a temperature range of 17-22 C and a pH of 6.5-7.0 for the species.

Spawning Behavior & Trigger

These fish are divers: the pair completely submerges into the soft bottom substrate to breed, releasing and burying eggs at various depths. A conditioned female will generally release her full complement of eggs over several hours. After spawning, the peat is poured through a fine net to capture the egg-laden medium.

Egg Diapause & Hatching

The collected peat is squeezed to remove as much water as possible, rolled in newspaper and allowed to dry until pinching it releases no water, then stored at room temperature. Annual killifish eggs pass through periods of diapause before they are ready to hatch. FishBase cites about three months of incubation for this species; Tropical Fish Hobbyist notes annual species generally take three to seven months or more depending on storage temperature. To hatch, the peat is wetted with soft water; ready eggs typically hatch within 24 hours.

Common Challenges

The chief difficulties are judging diapause length and keeping peat moisture correct: too wet risks fungus and premature development, too dry kills embryos. Because the species is annual and short-lived, replacement stock should be raised continuously from each spawning.