Breeding Maria's Rainbowfish (Melanotaenia maccullochi)
Breeding Melanotaenia maccullochi: sexing by male finnage and colour, conditioning, plant or mop spawning with daily eggs and rearing the fry.
Overview
Melanotaenia maccullochi is found in Papua New Guinea and Australia across habitats ranging from clear streams to tannin-stained ponds, reaching a maximum standard length of about 7 cm. Seriously Fish describes it as not a difficult species to breed, being an egg-scatterer, although the fry can prove somewhat tricky to raise.
Sexing
Males display more vibrant colouration and have elongated dorsal and anal fins, while females have a deeper body shape and stay plainer. The intensified colour and extended finnage of males make a conditioned spawning group easy to read.
Conditioning
The adults are best conditioned as a group in a separate aquarium with plenty of live and frozen foods. Good conditioning fills the females out and brings the males into constant display before spawning.
Breeding Setup
- Spawning occurs over fine-leaved plants or synthetic spawning mops, with no substrate required.
- A separate, well-oxygenated tank with gentle air-driven filtration works well.
- Keep the water clean and stable throughout the extended spawning period.
Spawning Behavior & Trigger
Pairs produce eggs daily over several weeks, with the eggs attached to surfaces by a small thread among the plants or mop. Rather than a single mass spawn, females release a steady trickle of eggs across the spawning period.
Egg & Fry Care
The eggs hatch in 7-12 days depending on temperature. The fry initially require infusoria-type foods before transitioning to free-swimming foods such as brine shrimp nauplii after about one week.
Common Challenges
Although spawning is easy, the small fry can be tricky to raise and depend on suitably tiny first foods and clean water. Moving the spawning medium to a rearing tank protects eggs and fry from hungry adults. Because the species ranges across very different waters in the wild, from clear streams to tannin-stained ponds, it adapts to a fairly broad range of clean, stable aquarium conditions for breeding rather than demanding one narrow profile, which makes consistent water quality and conditioning, rather than exotic chemistry, the main keys to success.