Melanotaenia

The New Guinea rainbowfish, Melanotaenia affinis, is a rainbowfish from Papua New Guinea. It was one of the first rainbowfish species to be imported for the hobby in any numbers. Three geographical variants are found in the hobby: the widespread 'standard' form, the 'Pagwi' form from a tributary of the Sepik River, and the 'Bluewater Creek' form known from a single location near Madang. They look superficially similar and differ only in small details of colour and patterning.

The western rainbowfish, Melanotaenia australis, is a rainbowfish from Australia and probably the commonest rainbowfish species there. Once classified in the M. splendida complex, it has since proved genetically distinct from that group, with two clear lineages within it. Colour and patterning vary widely by locality, and the different morphs should not be mixed in the aquarium because they hybridise freely. Juveniles are much drabber than adults, and full colour can take over 12 months to develop.

Boeseman's rainbowfish, Melanotaenia boesemani, is a rainbowfish from Indonesia, known only from the Ajamaru lakes and nearby Lakes Hain and Aitinjo. One of the most popular rainbowfish in the hobby, it is almost always sold as farmed stock from the Far East and Eastern Europe. The species is rare in nature and on the IUCN red list, and collection of breeding stock for the trade has had a massively detrimental effect on it. The drab juveniles usually offered for sale can take over 12 months to colour up.

The Australian rainbowfish, Melanotaenia fluviatilis, is a rainbowfish from Queensland and New South Wales, Australia. Also known as the Murray River or crimson-spotted rainbowfish, it is easily confused with the very similar M. duboulayi, with which it was once grouped as a single species. Its range extends further south than any other rainbowfish, and it can withstand relatively cool temperatures, though it becomes less active and loses colour if kept that cold.

The slender rainbowfish, Melanotaenia gracilis, is a small rainbowfish from the Drysdale and Carson Rivers in the Kimberley, north-western Australia. It is uncommonly seen in the hobby because it comes from such a remote area, and the IUCN lists it as at risk. Unlike many members of the genus, it lives in sparse, rocky, slow-moving stretches of river and in isolated pools during the dry season.

The Lake Tebera rainbowfish, Melanotaenia herbertaxelrodi, is a rainbowfish endemic to the Lake Tebera basin in the Central Highlands of New Guinea. It inhabits clear, heavily vegetated water in the lake and its surrounding streams, and is probably at risk from overfishing. Mature fish are among the more colourful rainbowfish, and they show their best colours in a heavily planted tank with high water quality.

The Irian Jaya rainbowfish, Melanotaenia irianjaya, is a rainbowfish from Indonesia, recorded only around Bintuni Bay in Irian Jaya. It can be identified by the longer middle rays in the dorsal and anal fins, a feature usually associated with the closely related genus Glossolepis. It is not often seen in the hobby. In nature it lives in slow and fast-flowing rainforest streams with little aquatic vegetation, using submerged logs and branches for cover.

The Lake Kutubu rainbowfish, Melanotaenia lacustris, is a rainbowfish endemic to Lake Kutubu and the River Soro in Papua New Guinea. The lake is threatened by overfishing, much of it for the aquarium trade, and by oil development, and the species has 'vulnerable' status on the IUCN red list. Juveniles are much drabber than the blue adults and are usually sold as 'blue' rainbowfish or similar. Full colour can take over 12 months to develop.

The dwarf rainbowfish, Melanotaenia maccullochi, is a small rainbowfish from Papua New Guinea and Australia. Several geographical variants are available, differing in colour, patterning and sometimes size, and they should not be mixed in aquaria because they may hybridise. Some are so distinct that they may turn out to be different species. It is found in a wide range of habitats, from clear streams to turbid, tannin-stained ponds.

The neon dwarf rainbowfish, Melanotaenia praecox, is a small rainbowfish endemic to the Mamberamo river system in New Guinea, Indonesia. It inhabits swiftly flowing tributaries of the main river and the surrounding swamps and marshes. Peaceful and small enough for many community aquaria, it shows its best colours in a heavily planted tank with floating plants to diffuse the light.

The checkered rainbowfish, Melanotaenia splendida inornata, is one of four described subspecies of M. splendida and comes from Australia. The subspecies differ mainly in colour, pattern and fin counts, though these also vary by locality, and the different forms should not be mixed in the aquarium because they may hybridise. Juveniles are much drabber than adults, and full colour can take over 12 months to develop.

The red-striped rainbowfish, Melanotaenia splendida rubrostriata, is a rainbowfish from Indonesia and Papua New Guinea. One of the most colourful of the four described subspecies of M. splendida, it lives among vegetation and debris in the tributaries and swamps of coastal plain rivers. The forms and subspecies should not be mixed in the aquarium because they may hybridise, and the drab juveniles can take over 12 months to colour up.

The eastern rainbowfish, Melanotaenia splendida splendida, is one of four described subspecies of M. splendida and comes from Australia. It varies widely in colour and patterning by locality, and fish are often sold with a place name added to the species name. The different forms and subspecies should not be mixed in the aquarium because they may hybridise. Full colour can take over 12 months to develop.

The banded rainbowfish, Melanotaenia trifasciata, is a rainbowfish from Australia, most commonly seen in flowing streams and tributaries. Colour and patterning vary widely by locality, and the morphs are often sold with the collection locality added to the scientific name. They should never be mixed in the aquarium because they hybridise freely. Several species are thought to be involved, and a reclassification will probably follow.