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NEW GUINEA RAINBOWFISH

Ruby Rainbows
Melanotaenia splendida rubrostriata

QUICK INDEX

Glossolepis incisus

Melanotaenia boesemani

Colour Changes in Rainbows

Melanotaenia lacustris

 

Melanotaenia parkinsoni

Melanotaenia maccullochi

Melanotaenia praecox

Melanotaenia s. rubrostriata

The material on these pages referring to Rainbowfish and their relatives was compiled from various sources, as part of my own learning experience, getting to know my fish from what other sources had to say about them. Pictures and text are used for educational purposes and with thanks. Additional comments are based on my own experience. I have placed these notes online as an adjunct to the educational material that I wrote on Ancient Gondwana Land cichlids and rainbowfish. This is not an exhaustive list but a showing of those species that I have kept and found suitable to my aquarium conditions.

Salmon-Red Rainbowfish - Glossolepis incisus (Weber, 1908); Salmon-Red Rainbowfish; Lake Sentani Red rainbowfish.

Description: large, deep bodied rainbowfish with small head, large eyes and silvery scales; adult males attain an all-over brilliant salmon-red colouring.

Distribution: Irian Jaya, W. New Guinea: endemic to Lake Sentani.
Natural Habitat: Lives along the shores of the lake near submerged vegetation.

Conservation Status: Unknown.
Threats: Habitat degradation and competition with introduced, exotic, feral species such as carp and Tilapia. Caught as a food source in Sentani, Irian Jaya. The lake is also no longer pristine and the pollution from settlements may endanger this fish.

Size: One of the larger rainbowfish, growing to 10 cms to 12+ cms.
Water Requirementshard freshwater, tropical, temperature range 25° - 30°C, pH 7.0 - 8.0; dGH range 9.0 - 19.0.
Tank Habitat: needs space; well planted aquaria with open spaces for swimming.
Diet: Omnivrous. Adapts to flakes and live foods.
Sexing:  Females silver/golden, slimmer in outline; breeding males salmon-red and much deeper bodied than females.  Females do not have red colour in any fins or on the body.
Reproduction
: Spawns in plant growth. Do not over-feed.
Tank Community: Ideal for a community of larger fish requiring similar conditions, such as other, large rainbows and mbuna that like hard water. Keep with fishes of a similar size (i.e. large when adult).
Incompatible Species:  Unknown. Looks after itself with fish of the same or similar size.

Comments: I have found this fish to be easily scared into jumping.  Provide cover and a quiet environment. Interestingly, while Max Weber discovered the fish early in the 20th C., it was not until 1973 that Glossolepis incisus were collected and made their way into the fish trade. It is a very desirable fish and ought to be protected and conserved.

G. incisus

Glossolepis incisus, male

This fish requires water that is alkaline and hard. It is an adaptable species, tolerating changes in water conditions, except for high ammonia/ammonium, nitrite and nitrate levels.

Young fish are all a dull, greenish olive colour with a trace of silvery sheen. Young males take time to develop their red colouring and juvenile males look much like female fish of this species. However, once the fish reach a length of 4 to 5 cm the males begin to progressively develop colour. The change is rapid, with full colour density reached by the time they are 7 to 8 cms long.  Females develop a yellowish olive body colour with a golden iridescence to the scales. Colour does not develop well if the water conditions are not correct. Other Glossolepis species are worth a try.

Boeseman’s Rainbowfish- Melanotaenia boesemani (Allen & Cross 1980); Lake Ajamaru Rainbowfish.

Description: large rainbowfish, with a laterally compressed, deep-set body and a relatively small head; vivid colour in mature males; iridescent scales; body appears bi-coloured dark, blue-green to the front, orange/yellow to the anterior and purplish above; greenish iridescence over body, especially along the upper dorsal side of the body; dorsal fin edged in white. Colour development is slow and varies with the mood of the fish and with water quality. This is an active, shoaling species.

Distribution: W. New Guinea, Irian Jaya; especially Lake Ajamaru, Irian Jaya, at the headwaters of the Ajamaru River (Vogelkop Peninsula) which drains into the Kais River, eventually flowing into the Ceram Sea to the south. Found mainly in Lake Ajamaru and a few surrounding tributaries, but it also occurs in Lake Hain and Lake Aitinjo.

Natural Habitat: Riverine, freshwater tropical. benthopelagic; freshwater; pH range: 7.0 – 8.0; dH range: 9 - 19
Conservation Status: Not in IUCN Red List.

Economic use: Commercial aquarium trade.
Threats:  Unknown.
Size: Approx. 9cms SL; 7 cm SL (female); males larger than females.

Water Requirements: reports vary: (1) "The lakes and streams are alkaline with pH in excess of 8.0. Heiko Bleher reported that he initially collected specimens in a small artificial pond constructed by the local natives. The water conditions recorded were reported as pH 9.0, hardness 5° dGH, and conductivity 145 mS. More specimens were collected later from a fast-flowing clear water creek near Ajamaru. Marinus Boeseman reported a pH of 6.4-6.5 when he collected his specimens."* See comments, at right. [* Source]

Tank Habitat: Planted tank with open swimming spaces. Good filtration required and temperature 25oC- 27oC; pH 7.2 - 8.0. Shows adaptability to pH  >7.2.

Diet: Small crustaceans and insect larvae such as mosquito and midge larvae; opportunistic feeders among plants and in open water; will eat frozen foods such as blood worms and brine shrimp; adaptable to flakes and granules. Captive specimens are are active feeders and leap at the food in a feeding frenzy.


Boeseman's Rainbowfish: Melanotaenia boesemani

Sexing:

Females display a broad, dark mid-lateral stripe accompanied by a series of narrow yellow or reddish-orange longitudinal stripes corresponding with each scale row, that deepen or lighten according to mood. Mature, older females often show colouration similar to subordinate males, but females are usually easily identified by a shallower body/chest depth and smaller, more rounded fin edges than males. Males are brighter and deeper bodied; first dorsal fin is longer in males and reaches the second dorsal fin; the dorsal fins on females do not meet. Young fish take some time to grow and show their distinctive colouring  but is developed by 4 cms size (usually).
Reproduction: dioecism, external, spawns in plant growth. 
Tank Community: Peaceful, active in shoals. Best kept in shoals of 6 or more. Frequent partial water changes are vital for care of this species.
CommentsOnce reported that this species is not suited to being kept in hard water with pH >7.2 (doubtless in deference to Boeseman's initial report of low pH values), it has become a popular pet species in Australia and is kept in a variety of water conditions, even in Sth Australia's notoriously hard, alkaline, tap water. Water must be well aged and nitrite free. Best kept in an established tank that has been running well for many months.
Keep these fish in shoals of 6+ with plant cover.

Colour flashes on Boeseman's Rainbowfish

A typical, adult, male M. boesemani is pictured at right. Like all Rainbowfish, the iridescence on the body of a live fish, flashes and changes in fractions of a second, as the iridiophores change appearance with the mood of the fish. In M. boesemani there is a bright, iridescent, green stripe or blaze running from the mouth, along the top of the head and back to the second dorsal fin. M. lacustris has a similar, bright, iridescent blaze that grades in colour from orange-tan to white. The picture, at right, clearly shows a pale, blue colour along the head of M. boesemani but does not capture the iridescence well. When viewed from above, this stripe is bright and very prominent. However, it is not always present. It comes and goes, brightens and flashes, with the mood of the fish. It varies in colour, too, from iridescent green to nearly white. I have seen a similar flashing stripe in M. lacustris, M. maccullochi, and M. splendens but of a different colour- bright golden-yellow in M. maccullochi and M. splendens. It is as though the fish turns on this iridescence in response to another fish (or me observing above him) as a signal. The only other animals that I have seen showing such a rapid flash of iridiophores are other rainbowfish, cichlids, leather-jackets and the marine Cuttlefish.

The Australian Museum fish site reports: "Many species of fishes however can change colour. The changes can be slow or fast. Slow changes of colour (eg breeding colouration) are generally under the control of hormones and are usually semi-permanent.

Rapid colour changes (eg stress responses) are largely under control of the nervous system although hormones may also be involved. The colour of fishes can also vary with the seasons, between day and night and even with changes in habitat and food.

There are two kinds of cells that give colour to fishes, chromatophores and iridiophores (also called iridocytes). The Chromatophores are located in the dermis of the skin, above or below the scales. They impart true colour (rather than structural colour) and contain black, red, yellow, blue, white (and rarely green) pigment granules called chromatosomes. Only one colour is found in each chromatophore. Colour changes result from chromatosomes concentrating in the centre of the chromatophore or dispersing throughout the cell.

Iridiophores contain highly reflective guanine crystals. The crystals act as mirrors, which reflect the colours of the outside environment. Iridiophores are responsible for the silvery appearance of many pelagic fishes." (Source)

The ability to change colour makes Boeseman's Rainbowfish fascinating to watch, as both the chromatophores and iridiophores constantly change to give a range of colour changes, depending upon time of day or whether the fish is feeding, courting or stimulated in some way.

The Lake Kutubu Rainbowfish- Melanotaenia lacustris (Munro 1964); The Cobalt Blue Rainbowfish; Turquoise Blue Rainbowfish.

   Melanotaenia lacustris, male, blue/silver

Melaenotaenia lacurtris, female; compare difference in body depth

Description: a medium sized rainbowfish, with a laterally compressed body and small head; coloured vivid blue in mature males; iridescent scales; overall silvery-blue body colour, darker above, pale below, with small, blue-black lateral line stripe at the tail end; a bright, iridescent stripe outlines the lateral line; fins blue outline in black. Has a bright, golden-tan to blue-white, iridescent line along the back, from mouth to dorsal fin, which is more or less present, depending on the mood of the fish. This blaze is tan to orange coloured at the head and grades to near white at the dorsal fin. The blaze along the upper edge of the body flashes colour with the mood of the fish. Depending on water conditions, captive environment and diet, Melanotaenia lacustris can display an array of different colours and patterns ranging from cobalt blue, steel blue, aquamarine through to lighter and darker shades of turquoise. When spawning the nape area changes to a bright orange or golden-tan colouration. Rows of orange-red dots between the rows of scales are present but not prominent.

Distribution: Southern Highlands of Papua New Guinea; found only in Lake Kutubu and the Soro River, which is the only outlet stream of the lake. The Soro River eventually flows into the Kikori River system. Lake Kutubu is a scenically beautiful crystal clear lake situated about 40 kilometres from Mendi, the main town of the Southern Highlands Province in central Papua New Guinea.

Natural Habitat: lake, freshwater tropical; temperature of water 21-25oC; benthopelagic; freshwater; pH range: 7.0 – 8.6; dH range: 9 - 19.
Conservation Status: Not in IUCN Red List.

Economic use: Commercial aquarium trade.
Threats:  Regarded as vulnerable in its endemic range; threatened by pollution from the Ok Tedi mining project which leaches heavy metals into the lake; also at risk by encroaching settlement.
Size: Approx. 10-12 cms; 7 cm SL (female); can grow to 11 - 13 cms TL but usually less than 10 cm;  males larger than females.

Water Requirements: clear, fresh water, temperature range of 21 to 25°C and a pH of 8.5-9.0.

Tank Habitat: Planted tank with open swimming spaces. Good filtration required and temperature 25oC pH 7.2 - 8.0.

Diet: Small crustaceans and insect larvae such as mosquito and midge larvae; opportunistic feeders among plants and in open water; will eat frozen foods such as blood worms and brine shrimp; adaptable to flakes and granules.

Sexing: Males are larger than females and have a deeper body and are more brightly coloured, with a body depth (dorsal to ventral) of 4-5 cm, much deeper bodied than females.
Reproduction: dioecism, external, spawns in plant growth. Spawning females produce between 100 and 200 eggs, spawning a number of times daily for several days. Eggs adhere to water plants and hatching occurs after 6-10 days, depending on temperature.
Tank Community: Peaceful, active in shoals.
Comments:  Best kept in shoals of 6 or more fish. They will shoal with other rainbows of a similar size. The fish shows a variety of colouration at different times of the day and can change colour rapidly, from blue, greenish and golden hues to shades of silver, cobalt blue and turquoise.  Their black colour intensifies at night.

 

Young fish and males display a bright, iridescent, white to golden-tan to white stripe along the head and back, which they flash when excited or displaying. The pictures at left and below, right, show the colour blaze, which is prominent at breeding and during displays by the fish. This flashing colour blaze is also shown in other species of rainbowfish to a greater of lesser degree.

 

 The Lake Kutubu Rainbowfish is something of a chameleon, with individuals changing colour rapidly, depending on water conditions, time of day and mood. The flashes of colour along the top of the body, from head to dorsal fin, as shown at left, is especially remarkable in this species. The colour blaze on the forehead varies from orange-tan to white and brilliant, colour flashes, in shades of yellow, green, blue, purple and violet, flicker on and off in fractions of a second. This behaviour is particularly noticeable in breeding males. See my article on "Colour Changes in Rainbowfish" for more comments.

 

This is an active species and swims in the middle ranges of the aquarium against any small current that is present. They are active jumpers and leap at food on the surface so that cover is essential. They are an easy species to keep, in my experience, and do not require high water temperatures.

M. lacustris, male cobalt blue

M. lacustris, male, turquoise, gold and black, showing blaze on head

Parkinson’s Rainbowfish- Melanotaenia parkinsoni (Allen & Cross 1980) .

Description: a relatively slender, medium sized rainbowfish, with a laterally compressed body and small head; vivid colour in mature males; iridescent scales; overall silvery body colour with a rosy "chest" and narrow orange stripes between the scale rows. The fins of adult males are bright orange (or yellow) with dark edges. The posterior half of the adult male body has patchy, orange or yellow bars. Sometimes the bars or blotches fuse to cover the entire posterior half of the body. Colour development is slow. Selected "forms" include deeper yellow and orange coloured fish.

Distribution: Southern Papua New Guinea; found along the southern coast of eastern Papua New Guinea between the Kemp River and Milne Bay.

Natural Habitat: Riverine, freshwater tropical, 27-30°C; benthopelagic; freshwater; pH range: 7.06 – 8.0; dH range: 9 - 19. Found in streams in a grassy plains habitat with patchy rainforest immediately adjacent to the creeks. The waters are subject to seasonal low water during the dry season.
Conservation Status: Not in IUCN Red List.

Economic use: Commercial aquarium trade.
Threats:  Unknown.
Size: Approx. 11.0 cm SL (male/unsexed; 9.0 cm SL (female); not as deep bodies as some rainbowfish.

Water Requirements: tropical, freshwater tropical, 27-30°C; pH 7.6 - 7.8; alkaline water.

Tank Habitat: Planted tank with open swimming spaces. Good filtration required and temperature 25oC- 27oC,  pH 7.4 - 7.6.

Diet: Small crustaceans and insect larvae; will eat flake foods, blood worms and daphnia; adaptable to flakes and granules. Some vegetable matter in the diet in necessary and Spirulina Flakes and/or skinned green peas do well for this.

Sexing: Females dull; males develop brighter yellow colouration and pinkish "chest". Some males show longer dorsal fins with thread-like tips.  Reproduction: dioecism, external, spawns in plant growth. Spawning females producing between 20-50 eggs each day for several days. Eggs adhere to fine-leaved plants or among the roots of floating vegetation. Hatching occurs in about 8 to 10 days at temperatures between 24-28°C.
Tank Community: Females are peaceful, active in shoals; males reputedly more aggressive than other Melanotaenia sp. and can be territorial to other male rainbowfish, resulting in threat displays. Fish are seldom injured in confrontations. Best kept in large, well planted tanks, at about 27°C in shoals of 6 or more. Needs swimming space and cover.

Melanotaenia parkinsoni (male) with more typical colouring.

 

Melanotaenia parkinsoni (male) showing more colour than usual.

 

Comments

Young fish take some time to grow and show their distinctive colouring.

Select a shoal of fish about the same size; does well with other Rainbows from New Guinea and will shoal with them.

Macculloch's Rainbowfish - Melanotaenia maccullochi (Ogilby, 1915)  
Description: A small rainbowfish, with laterally compressed body. Several geographically isolated populations are found in New Guinea, Northern Territory, northern Queensland. The dorsal and anal fins are orange-red with a lower black margin running along the body line. The dorsal edge of the fish has a bright, iridescent stripe. The caudal fin has a fan of orange-red colouration. Females are much less colourful, though some do show a hint of the male's coloration. Females tend to grow larger and have deeper bodies than males.

Species Diagnosis: Dorsal spines (total): 5-8; Dorsal soft-rays (total): 7-12; Anal spines: 1-1; Anal soft-rays: 13-19.
Distribution: Australasia; Papua New Guinea (lower and middle sections of the Fly River westward to the Bensbach River) and north-eastern Australia. Natural Habitat: benthopelagic; freshwater; pH range: 7.0; dGH range: 10.0; Climate: tropical; 20 - 25°C. Inhabits lowland swamps and small streams, usually in clear, acidic waters with ample cover in the form of log debris or aquatic vegetation.
Conservation Status: Not in IUCN Red List. Threats:  Habitat degradation.
Size: Max. size: 6.0 cm SL

Water Requirements: tropical freshwater 20 - 25°C.; pH range: 7.0; dGH range: 10.0;
Tank Habitat: dense planting, with open swimming places and logs to provide cover. Neutral water around 24°C and good water quality.
Diet: Omnivorous. Adapts to flakes and responds to occasional feedings of live foods.

Sexing: Males have a deeper body profile and longer fins.

Reproduction: dioecism, external, non-guarders.

M. maccullochi Photo Neil Armstrong

Tank Community: Makes a good community fish with other rainbows and gudgeons requiring similar water conditions.
Incompatible Species: Rainbowfish that prefer alkaline water; larger fishes;  Arowanas (Yes, mine swallowed them in one gulp when he grew big enough and decided that his tank mates were food).
Comments: Specimens from New Guinea show deeper colours than the Australian form. Can be kept with other small rainbowfish such as M. praecox. I have not kept the Papua New Guinea species. The Australian form from Harvey Creek seems adaptable to water conditions from soft to moderately hard, pH adjusted to 70. - 7.4.

 Dwarf Neon Rainbowfish - Melanotaenia praecox (Weber & Beaufort 1922) syn. Rhombatractus praecox, Nematocentris praecox.

Description: Slender, laterally compressed fish, with marked narrowing at the beginning of the caudal fin; bright iridescent colour with "neon" blue line along the back.  Male brighter, with dorsal and anal fins edged in red.

Distribution: Endemic to New Guinea and Irian Jaya (Mamberano River).

Natural Habitat: Riverine, with bushy plant cover.
Conservation Status: Unknown.
Threats:  Unknown.

Size: Approx. 6.0 cms. One of the small Rainbowfish.
Water Requirements: Flowing, clean freshwater; Soft and slightly acidic (pH 6.8 - 7.0); adaptable to near neutral water. Temperature 25- 27oC.  Good filtration required.

Tank Habitat: Well planted tank with open swimming spaces.
Diet: Small crustaceans & insect larvae; will eat flake foods, blood worms and daphnia
Sexing:  Males bright, iridescent blue, with red edges to fins, slight humped back; females paler blue with yellow fins.  Both sexes show little colour until 2-3 cms in size.
Reproduction: Readily spawns in plant growth. Parents ignore the fry and do not eat them.


Dwarf Neon Rainbowfish

Tank Community: Generally peaceful, shy but active in shoals; keep with small fish or in species tank. Some males chase other fish away from desired females.
Comments:  Easily scared into a "comatose" fit!  Keep these fish in shoals of 6+ with plant cover. This species has a reputation for being delicate and subject to bacterial infections. Tank bred specimens may be hardier. May be kept with other dwarf rainbows, Cardinal Tetras and Red-line Rasboras to good effect, in a well planted aquarium.

Red-striped Rainbow Fish - Melanotaenia splendida rubrostriata (Ramsay & Ogilby, 1886); Ruby Rainbowfish.

Description: laterally compressed, deep set rainbowfish with a small head; upper body has iridescent, bluish scales and five, longitudinal orange/red to salmon pink stripes running from behind the head to the tail and reaching to the mid-line of the body below which is another four or five less prominent or broken stripes extending across the pale belly; fins red edged in black with bright blue spots and dashes between the red rays; variable rainbow colours in males c.f females; colour between stripes varies with mood- silver grey in calm mood, silvery sky-blue to violet in excited specimens.
Distribution: South of the dividing range in New Guinea and Irian Jaya, from between the Aramia River (near the Fly River) of Papua New Guinea and Etna Bay in central Irian Jaya, Indonesia and also the Aru Islands in the Arafura Sea and Daru Island near Torres Strait.
Natural Habitat
: Riverine, coastal lowlands and swamps around submerged branches and vegetated swamps. Waters are soft, with pH range: 5.6 – 7.4. Temp. 25-30oC.
Conservation Status: Unknown.
Threats:  Unknown.
Size: Approx. 6.0 to 12 cms.

Water Requirements: Freshwater; Soft and slightly acidic (6.8 - 7.0); adaptable to near neutral water. Temperature 25- 27oC. Good filtration required.
Tank Habitat: Planted tank with open swimming spaces; some natural light.
Diet: Small crustaceans and insect larvae, vegetable matter- algae and Duck Weed; will eat flake foods, blood worms and daphnia; adaptable to flakes and granules.

Sexing: Males brighter and deeper bodied; first dorsal fin longer in males and reaches the second dorsal fin- in females it does not.

Ruby Rainbows
Melanotaenia splendida rubrostriata

 

Reproduction: Spawn in plant growth. Spawning usually occurs from October to December, with females producing between 100 and 200 eggs, spawning a number of times daily for several days. Eggs adhere to fine-leaved plants or among the roots of floating vegetation with hatching occurring after 6-7 days.
Tank Community: Generally peaceful, active in shoals. Keep in shoals of 6 or more.
Comments:  Keep these fish with plant cover. As this fish is a shoaling species, it is best kept in groups of 6 or more.
 


Link to Notes on Keeping Australasian Blue-eyes- also related to the the Rainbows.

Link to Notes on Keeping Australian Rainbowfish

Link to Notes on Fishkeeping

Breeding Rainbows

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