Breeding Lake Tebera Rainbowfish (Melanotaenia herbertaxelrodi)

How to breed Melanotaenia herbertaxelrodi: sexing, conditioning, plant or mop spawning, eggs hatching in 7-12 days and rearing the tiny fry.

Overview

Melanotaenia herbertaxelrodi is a rainbowfish endemic to the Lake Tebera basin in Papua New Guinea, listed as Vulnerable on the IUCN Red List. Like other members of the genus it is an egg-scatterer: spawning is described as relatively straightforward, although raising the fry can prove the harder part of the project. Because the species is restricted to a single basin, captive breeding also helps maintain aquarium stocks without further pressure on wild populations.

Sexing

Mature males are larger and more brightly coloured than females, with deeper bodies and longer dorsal and anal fins. Females stay slimmer and plainer. Dominant males intensify their golden colour and display constantly when ready to spawn.

Conditioning

Condition the adults as a group in a separate aquarium using plenty of live and frozen foods until the females fill out noticeably and the males display continuously. The species is omnivorous and accepts dried, frozen and live foods, with live foods improving colour and condition before spawning.

Breeding Setup

• Spawning tank around 30 inches (about 75 cm) or larger, no substrate required.
• Fill it with fine-leaved plants such as java moss, or use nylon spawning mops.
• Maintain slightly hard, alkaline water around pH 7.5 and a warm temperature.
• A small air-powered filter provides gentle oxygenation and flow.

Spawning Behavior & Trigger

Conditioned pairs spawn over the plants or mops, attaching eggs to the medium by fine adhesive threads. Females release small numbers of eggs at a time, continuing daily over an extended period rather than in a single large batch. The eggs hang among the fine leaves until they develop.

Egg & Fry Care

Eggs hatch in roughly 7-12 days depending on temperature. The tiny fry first need infusoria-type foods, then graduate onto free-swimming foods such as brine shrimp nauplii after about a week. Mops or plants can be moved to a separate rearing tank to protect eggs and fry from being eaten.

Common Challenges

The main difficulty is rearing the very small fry, which require infusoria-sized first foods and stable, clean water before they can take larger prey. Adults may also eat eggs, so spawning media should be removed for hatching.