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Rainbowfish / Melanotaeniinae / Dark Rainbowfish

Dark Rainbowfish
Melanotaenia nigrans

Physical description:  An elongated, laterally compressed species with a large eye.   There are two dorsal fins, an anal fin with a long base, and a slightly forked caudal fin.  The back is yellow-gray and the belly is beige-white.   The flanks are marked with a violet to green iridescence.  A dark, black band runs from the snout through the eye and to the caudal fin.   Bordering this marking are regions of whitish-yellow.  The fins, except for the caudal, are violet in color with dark borders.   The caudal fin may be reddish-yellow.
Size/Length: Males to 2.8" (7 cm), females to 2.4" (6 cm)
Similar species: Melanotaenia fluviatilis, M. maccullochi
Habitat: Inhabits freshwater rivers and occasionally visits brackish water estuaries.   Eastern Australia; from Sydney to the Cape York Peninsula; and Papua New Guinea.
S: middle, top
Aquarium: A tank measuring 32" (81 cm) with a capacity of 30 gallons (114 L) is sufficient.   Plant along the edges of the tank and leave an open swimming area.   The lighting should be bright and a sandy or fine gravel substrate can be used. 
Water chemistry: pH 6.7-7.8 (7.2), 8-15 dH (10), 64-77°F (18-25°C).   Salt can be added, anywhere from a 0.5-1.5% addition is acceptable.
Social behavior: An active, but peaceful schooling species that should be kept in groups of five or more.
Suggested companions: other Rainbowfish, Barbs, Danios, tetras, Gouramis, Corydoras, Livebearers
FOOD: Live; insect larvae, crustaceans, worms, insects; flakes
SEX: Males are larger and more colorful with pointed first dorsal fin.   Females lack the black edging to the fins.
Breeding techniques: As for M. fluviatilis.   The parents will ignore the eggs.
Breeding potential: 5.  An easily bred fish.
Remarks: In tanks without males, a female may lay mature eggs which will not hatch.
Difficulty of care: 4.  This robust species is suitable for a community tank.


By Rhett Butler   Mongabay.com