Slender Rainbowfish, Melanotaenia gracilis Allen 1978

Other Names: Slender Rainbow Fish

Slender Rainbowfish, Melanotaenia gracilis. Source: Rudie H. Kuiter/Aquatic Photographics. License: All rights reserved


A pale greenish to olive-brown rainbowfish with an indistinct dark midlateral stripe and an iridescent lavender sheen on lower sides. The fins are transparent to slightly pink, and males usually have a red margin on the dorsal and anal fins, and red tips on the tail.

Mature males are usually much larger and deeper bodied than females.

Video of Slender Rainbowfish

Cite this page as:
Martin F. Gomon & Dianne J. Bray, Melanotaenia gracilis in Fishes of Australia, accessed 25 May 2024,

Slender Rainbowfish, Melanotaenia gracilis Allen 1978

More Info


Known only from King Edward River and Drysdale River system of Western Australia.

Inhabits clear freshwater river channels with still or slow-flowing water and usually lined with paper bark (Melaleuca) trees and Pandanus palms. Forms large schools in shady pools around submerged vegetation and woody debris at temperatures of 23°-28°C.


Meristic features:
Dorsal-fin rays: IV-VI; I, 7-10
Anal-fin rays: I, 17-20
Pectoral-fin rays: 12-15
Body relatively slender, elongate and laterally compressed; greatest body depth (adults > 50 mm SL): males 25.9-34.9, females 23.5-27.5; head length 23.4-26.3 in SL; snout length 6.6-7.9 in SL; eye large, diameter 6.9-9.4 in SL; jaw teeth conical, vomer with a solid band of well-developed teeth; teeth present on palatines; lateral line absent.

Scales large, horizontal scale rows 9 or 10; vertical scale rows 33 to 35.

Two separate dorsal fins, 1st originating behind the origin of the anal fin; anal fin long based; caudal fin forked.


Males to about 75 mm SL; females to about 65 mm SL.


Back and upper sides greenish or olive brown becoming mauve below with a dark mid-lateral stripe; fins with a yellowish tinge; males with a red margin on dorsal and anal fins and red tips on caudal fin lobes.


Little is known of the feeding habits of this species although food itmes probably include aquatic and terrestrial insects, small crustaceans and some algae.


Although the reproductive biology isunknown but it is likely they release dem, females likely produce eggs with adhesive threads that attach to vegetation.


  • EPBC Act 1999 : Not listed
  • IUCN Red List : Near Threatened (Lower Risk)
  • Remarks

    Co-occurs with Melanotaenia australis.

    Species Citation

    Melanotaenia gracilis Allen, 1978, Trop. Fish Hobbyist 26(10): 98. Type locality: Drysdale River, Western Australia.


    Martin F. Gomon & Dianne J. Bray

    Slender Rainbowfish, Melanotaenia gracilis Allen 1978


    Allen, G.R. 1982. Inland Fishes of Western Australia.  Perth : Western Australian Museum 86 pp.

    Allen, G.R. 1989. Freshwater Fishes of Australia.  Neptune, New Jersey : T.F.H. Publications pp. 1–240

    Allen, G.R. & Cross, N.J. 1982. Rainbowfishes of Australia and Papua-New Guinea. New Jersey : T.F.H. Publications 142 pp. figs.

    Allen, G.R., Midgley, S.H. & Allen, M. 2002. Field guide to the freshwater fishes of Australia.  Perth : Western Australian Museum 394 pp.

    Axelrod, H.R., W.E. Burgess, N. Pronek & J.G. Walls. 1991. Dr. Axelrod's Atlas of freshwater aquarium fishes. Sixth edition. T.F.H. Publications, Neptune City, New Jersey.

    Leggett, R. & Merrick, J.R. 1987. Australian Native Fishes for Aquariums.  Artarmon : J.R. Merrick Publications 241 pp. 142 figs.

    Merrick, J.R. & Schmida, G.E. 1984. Australian Freshwater Fishes Biology and Management. Sydney : J.R. Merrick 409 pp. figs 280 col. figs.

    Morgan D., D. Cheinmora, A.Charles, P. Nulgit & Kimberley Language Resource Centre. 2006. Fishes of the King Edward and Carson Rivers with their Belaa and Ngarinyin names. Land and Water Australia Project No. UMU22

    Quick Facts

    CAAB Code:37245008

    Conservation:IUCN Near Threatened

    Fishing:Aquarium fish

    Habitat:Clear freshwater rivers

    Max Size:7.5 cm SL


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