Breeding Lake Wanam Rainbowfish (Glossolepis wanamensis)

Breeding the critically endangered Glossolepis wanamensis: sexing emerald males, plant or mop spawning, fry care and its conservation role.

Overview

Glossolepis wanamensis is known only from Lake Wanam, a roughly circular high-altitude lake about 24 km west of Lae, Papua New Guinea. FishBase records a maximum length of 9.0 cm and lists it as Critically Endangered, noting it has virtually disappeared from the lake because of competition from introduced tilapias, while captive populations persist. It is described as an egg-layer, making aquarium breeding important for keeping the species available.

Sexing

As in the genus Glossolepis, males develop the deeper body and far more intense colour, with brilliant emerald-green flanks and fine dark fin edging, while females stay smaller and plainer. Dominant males display the strongest colour when courting.

Conditioning

FishBase describes the species as omnivorous; condition a group on varied live and frozen foods until the females fill with eggs and the males colour up and display steadily.

Breeding Setup

• Use fine-leaved plants such as java moss or nylon spawning mops over a bare base.
• FishBase gives a water profile of pH around 7.8 with hardness near 15.
• FishBase lists a temperature range of 26-30 degrees C.
• The natural habitat includes rocks, vegetation and driftwood cover.

Spawning Behavior & Trigger

As an egg-layer of the rainbowfish family it scatters adhesive eggs into the plants or mop, the eggs attaching by fine threads and being released over a period of days rather than in a single spawn.

Egg & Fry Care

Move the spawning medium to a separate tank to protect the eggs and fry. As with related rainbowfish, the small fry begin on infusoria-type foods and move onto free-swimming foods such as brine shrimp nauplii once large enough.

Common Challenges

Because the species is Critically Endangered with only captive stocks safeguarding it, keeping pure, well-recorded lines and avoiding hybridisation with other Glossolepis is essential. Its decline came from competition with introduced tilapias in its single small lake, so aquarium populations now act as a genetic reservoir for a fish that has virtually disappeared from the wild. Clean, warm, slightly alkaline water matching the FishBase profile and small first foods support fry survival.