Turquoise Rainbowfish (Melanotaenia lacustris) Breeding Guide

Breeding Melanotaenia lacustris: a continuous egg scatterer that lays thread-attached eggs daily onto plants or mops over weeks, with simple infusoria-then-Artemia fry care.

Overview

Melanotaenia lacustris is endemic to Lake Kutubu and the River Soro in Papua New Guinea and reaches about 12 cm. It is described as not a difficult species to breed, being an egg scatterer onto fine-leaved plants or spawning mops.

Sexing

Mature males are larger and more brightly coloured than females, and develop a much deeper body as they grow. When in condition, males also display an orange patch above the gill flaps.

Conditioning

Bring adults into condition before spawning; conditioned males show the characteristic orange head patch that signals readiness. A varied diet supports egg production over the extended spawning period.

Breeding Setup

Use a spawning tank of at least about 75 cm in length with slightly hard, alkaline water of around pH 7.5 and a temperature of roughly 22-24 °C. Provide fine-leaved plants such as java moss or spawning mops as an egg-laying substrate; no substrate is needed on the base.

Spawning Behavior & Trigger

The pair spawn over a period of several weeks, laying batches of eggs each day. The eggs are attached to surfaces such as the plants or mops by a small thread.

Egg & Fry Care

Eggs hatch in 7-12 days depending on temperature. The fry initially require an infusoria-type food before graduating onto free-swimming foods such as brine shrimp nauplii after a week or so.

Common Challenges

Because eggs are laid continuously over weeks, mops or plants must be checked and rotated regularly so that early eggs are not eaten and fry of similar age can be reared together. Matching the slightly hard, alkaline water the species prefers also supports good hatch rates.