Celebes Rainbowfish Breeding Guide

How to breed the Celebes rainbowfish (Marosatherina ladigesi): sexing, hard alkaline spawning water, mop or moss egg-laying, and rearing the tricky early fry.

Overview

Marosatherina ladigesi is a slender rainbowfish endemic to Sulawesi. It is not a difficult species to breed, being an egg-scatterer that lays a few eggs daily over several weeks, but the early-stage fry can be tricky to raise.

Sexing

Males are the more colourful sex and develop elegant extensions to the second dorsal and anal fins. Conditioned females appear noticeably plumper than males.

Conditioning

Condition the adults as a group in a separate aquarium with plenty of live and frozen foods. As they come into condition the females fill out with eggs. A ratio of two to three females per male is recommended.

Breeding Setup

Use a breeding tank at least 18 inches long with no substrate, furnished with fine-leaved plants such as java moss or nylon spawning mops. The water should be slightly hard and alkaline with a pH around 7.5 and a temperature of about 22 to 23 degrees Celsius.

Spawning Behavior & Trigger

A pair spawns over a period of several weeks, laying batches of eggs each day that are attached to surfaces by a small thread. The adults tend to eat the spawn, so eggs or mops should be removed to a separate hatching container.

Egg & Fry Care

Eggs hatch in five to ten days depending on temperature. The minute fry initially require infusoria-type food before graduating to free-swimming foods such as brine shrimp nauplii after a week or so. Stable water quality is essential during these early days.

Common Challenges

The main difficulty is the small size and sensitivity of newly hatched fry, which need infusoria before they can take Artemia. Protecting eggs from being eaten and supplying the correct first foods are the two decisive factors.