Rainbowfishes are the largest family of freshwater fish inhabiting the Australian-New Guinea region. They are found in rivers, lakes, streams, grassy swamps, lily lagoons and billabongs. Some individuals have even been collected from coastal streams that have brackish tidal influence. Such diverse environmental conditions have meant that rainbowfishes have learned to adapt to the different conditions and it is this adaptability that makes them ideal aquarium fish. The first rainbowfish was scientifically described in 1843 from an Australian collection made near the city of Darwin, in the Northern Territory early in 1840. They were named Atherina nigrans by John Richardson from the British Museum of Natural History in London. In 1894, Thomas Gill, an American ichthyologist, placed them in the genus Melanotaenia where they reside today. The genus name Melanotaenia was in reference to the very distinct black lateral line.

All Rainbowfishes found in Australia and New Guinea belong to the family Melanotaeniidae, and are arranged in six genera; Cairnsichthys, Chilatherina, Glossolepis, Iriatherina, Melanotaenia and Rhadinocentrus. Melanotaenia has the largest number of members and with the genus Iriatherina, are found in both Australia and New Guinea. Chilatherina and Glossolepis are endemic to New Guinea while Cairnsichthys and Rhadinocentrus are endemic to Australia.

Rainbowfishes were being maintained in the Australian aquarium hobby as early as the beginning of this century. In 1927, a number were sent by steam ship from Australia to Germany and were later bred by the Berlin Aquarium. It is believed that from this initial shipment, that rainbowfishes were first introduced to the organized aquarium hobby throughout Europe, and then to North America. In 1930 a number of rainbowfishes were collected in the Mississippi River. This was one of the earliest reports of an introduced ornamental fish found in the USA.

In the early days rainbowfishes were commonly known as sunfishes. When exactly they were called rainbowfishes nobody really knows. In January 1934, National Geographic Magazine ran an article written by Walter H. Chute, then director of the Shedd Aquarium in Chicago USA, called "Tropical Fish Immigrants Reveal New Nature Wonders" in which appeared a reference to the Australian Rainbowfish. However, the earliest report of them being called rainbowfishes that I can find was in an excursion report of the Aquarium & Terrarium Society of Queensland in March, 1932. This report was written by Amandus Rudel, a founding member of the Society. Speaking of rainbowfishes, Amandus said "I was astonished at the beauty of this fish the first time I saw it. Like a living rainbow, there is no other fish which can compare with its beauty. Naturally it has been my favorite ever since".

Although rainbowfishes have been available in the aquarium hobby for many years they never became commonplace on the international scene. This I believe was mainly due to their limited availability during the 1930's and the ensuing war years which saw a decline in the aquarium hobby. Availability never improved after the war years until breeders in Singapore started shipping specimens in the late sixties and early seventies. However, most of the rainbowfishes that were being sold in the aquarium trade during this period were a colourless assortment that looked nothing like the real species. Since the mid 1970s however, their popularity has grown tremendously, due in part to the efforts of Dr. Gerald R. Allen, an American ichthyologist who now calls Australia home. He has discovered and described many new species since 1974 and is recognized as a rainbowfish specialist. Heiko Bleher, an intrepid fish collector from Frankfurt, Germany started distributing new rainbowfish species collected mainly from New Guinea in the early eighties. ANGFA, the Australia New Guinea Fishes Association, was formed in 1982 to promote the aquarium keeping and breeding of rainbowfishes. Other specialist rainbowfish associations followed, and are established in Germany, the USA and Britain.

Keeping Rainbowfishes

To fully understand the maintenance of rainbowfishes in captivity you need to know some basic information about their natural environment. Rainbowfishes live in the tropical and sub-tropical climates of Australia and New Guinea. New Guinea is the second largest island in the world and lies south of the equator and north of Australia. Papua-New Guinea occupies the eastern half of the island, with the Indonesian province of Irian Jaya occupying the western half. Three quarters of the country is covered by tropical rainforests and the remainder consists of flat grassland, lowland floodplains and mangrove swamps. The climate is typically hot, humid and wet year round. Air temperatures on the coastal plains are reasonably stable all year (between 25 and 30 degrees Celsius). However, temperatures drop at higher altitudes and can be very chilly, especially in the Highlands. The temperature dropping progressively as altitude increases; down to mean annual temperatures of around 12 degrees Celsius at 3000 meters.

In Australia, rainbowfishes generally occupy three broad climatic zones. Above the Tropic of Capricorn has a tropical climate characterized by a generally hot, humid summer with strongly seasonal rainfall, and a dry, mild to warm winter. The climate is characterized by a distinct wet season with mean rainfall of 600-1600 mm over 4-7 months, followed by a dry season during which almost no rain falls. The environment of the wet/dry tropics are markedly different from that of the humid tropics one finds in New Guinea. Below the Tropic of Capricorn is sub-tropical with a similarly hot, humid summer and seasonal rainfall, but with some significant rainfall occurring during the mild winter. The interior portion of Australia occupied by rainbowfishes experiences an arid sub-tropical climate; summers can be extremely hot and dry, with variable rainfall; winters are cool to warm and dry, with irregular light rain. The freshwater environments of Australia and New Guinea contain mostly soft water, but their pH and clarity will vary according to their sediment content and the terrain over which they flow.

Keeping rainbowfishes healthy and happy in the aquarium requires a basic understanding of water quality. Water quality determines not only how well they will live and grow in the aquarium, but whether or not they even survive. Some water quality factors are more important such as soluble waste levels, dissolved oxygen, pH and temperature. Others, such as hardness and alkalinity have some affect, but are usually not critical. Acceptable water chemistry for rainbowfishes in captivity is a pH range of 6.5 to 7.8 and a general water hardness below 250 ppm. You should find that most domestic tap waters once treated for chlorine or chloramine removal will be suitable for maintaining rainbowfishes. Regular testing of your aquarium water and your tap water is also important as this will allow you to detect and correct any problems before your fish are adversely affected. However, the single most important factor for the successful maintenance of rainbowfishes in captivity is regular water changes. Ideally, 20 to 50 percent should be changed weekly. Regular water changes can mean the difference between success and failure for many aquarium fish species.

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