Breeding Painted Rainbowfish (Melanotaenia picta)

Breeding Melanotaenia picta from the Aru Islands: sexing by male finnage, plant or mop spawning, threaded eggs and rearing the small fry.

Overview

Melanotaenia picta is a rainbowfish from the Mareremar River system on Kobroor Island in the Aru Islands, Indonesia, where it lives in small rainforest brooks with quiet pools interspersed with cascades up to 3-4 m high and excellent water clarity. According to FishBase the stream channels are formed of relatively smooth limestone with little aquatic vegetation but plenty of log-snag shelter, and the species sits at a low trophic level around 2.9, feeding on small organisms. FishBase gives a maximum length of 9.3 cm for males and 7.9 cm for females and lists the species as Least Concern. As a member of Melanotaenia it is an egg-scatterer.

Sexing

In line with the genus, males grow larger and more colourful than females, developing deeper bodies and more extended dorsal and anal fins, while females remain slimmer and plainer.

Conditioning

Condition a group on varied live and frozen foods until the females round out with eggs and the males display strongly. Clean, clear water echoing the species' clear-brook habitat suits conditioning.

Breeding Setup

• Use fine-leaved plants such as java moss or nylon spawning mops; no substrate is required.
• FishBase describes the natural habitat as clear, limestone-channelled rainforest brooks.
• Provide gentle air-driven filtration and stable, well-oxygenated water.

Spawning Behavior & Trigger

Like other rainbowfish, conditioned pairs scatter adhesive eggs over the spawning medium, the eggs attaching by fine threads and being released over a series of days rather than in a single batch.

Egg & Fry Care

Move the spawning medium to a rearing tank to protect the eggs. As with related species, the small fry begin on infusoria-type foods before moving onto free-swimming foods such as brine shrimp nauplii.

Common Challenges

The fry are small and need tiny first foods and clean, stable water. Adults may eat eggs and fry, so separating the spawning medium improves yields. FishBase rates the species' population resilience as medium, with a minimum doubling time of about 1.4-4.4 years, so a steady, continuous spawning approach over weeks builds numbers more reliably than expecting a single large hatch.