Boitone's Pearlfish Breeding Guide

How to breed Simpsonichthys boitonei, a Brazilian annual killifish that buries its eggs in peat for a two-to-six-month dry diapause before wetting to hatch.

Overview

Simpsonichthys boitonei is a small Rivulidae killifish from the upper Parana River basin in Brazil. It is an annual species of seasonal pools and reaches about 5.5 cm total length. FishBase describes it as a bottom spawner with around two months of incubation and lists it as Endangered on the IUCN Red List.

Sexing

Males are the brightly coloured sex; females are plainer. A single male with one or two well-fed females makes a good spawning group, kept in their own breeding container rather than a community tank.

Conditioning

Tropical Fish Hobbyist advises isolating the breeders and preconditioning them with live or high-quality frozen foods for about a week before spawning to greatly raise the chance of success. The species is carnivorous.

Breeding Setup

Annual Simpsonichthys spawn into a soft substrate. Tropical Fish Hobbyist recommends a good grade of fertiliser-free peat moss or fibre, boiled briefly to sterilise it and ensure it sinks. The breeders are added over the settled peat and the container is covered. FishBase lists 20-24 C and notes aquarium conditions of about pH 6.6, hardness 6 and 24 C.

Spawning Behavior & Trigger

The pair dives into the peat to spawn, burying eggs within it. Tropical Fish Hobbyist reports that the female generally releases her full complement of eggs within about eight hours, and at most around twenty-four hours. After spawning the peat is poured through a fine net to capture the egg-bearing medium.

Egg Diapause & Hatching

The peat is squeezed dry, rolled in newspaper and dried until pinching it yields no water, then stored at room temperature. Annual eggs pass through several diapause periods before hatching. Tropical Fish Hobbyist gives an incubation range of roughly two to six months depending on species and storage temperature, consistent with the two months FishBase cites for this species. The peat is then wetted with soft water; ready eggs hatch within about 24 hours, sometimes sooner.

Common Challenges

Diapause timing and peat moisture are the main hurdles, as with all annuals. Because the species completes its life cycle within a year and is of conservation concern, maintaining a continuous breeding line is important for keeping captive stock going.