Home / Fishes / Silversides and rainbowfish / Murray River rainbowfish
No federal permit to keepMurray River rainbowfish
Melanotaenia fluviatilis
Fishes › Silversides and rainbowfish (Atheriniformes) › Melanotaeniidae (Rainbowfish)
The Murray River rainbowfish (Melanotaenia fluviatilis), known less commonly as the Australian rainbowfish, is a species of freshwater fish endemic to southeastern Australia.
Care at a glance
Species-specific aquarium care
- Tank: At least 24 in long and 12 in front to back for one adult (adults commonly reach about 3.3 in / 8.5 cm; the largest recorded was 4.3 in).
- Water: Freshwater.
- Temperature: 72–77°F (range recorded for this species).
- Layout: Uses both the bottom and open water: give open swimming space plus cover near the substrate.
- Availability: Rarely or never seen in the aquarium trade; expect to source it from specialists or not at all.
Calculated from this species' own FishBase record: tank size from its typical adult length and swimming zone, water values from its recorded ranges. The group guide below fills in general care.
Care guide
Species care notes
- Tank: a base of at least 35 × 12 in (roughly 21 US gallons); space needed is rated “large tank”.
- Water: a fairly wide range, from slightly acidic to slightly alkaline, 68–77 °F, pH 6.5–8, 8–20 dGH.
- Behaviour: temperament peaceful; a shoaling fish best kept in a group of six or more.
- Difficulty: Easy (Seriously Fish rating).
Short excerpts from the species profile:
- Setup: “This species, like most rainbows, looks most at home in a planted aquarium.”
- Diet: “Unfussy and will accept most dried, frozen and live foods.”
- Tankmates: “Very peaceful but can disturb smaller or slow-moving fish with its rapid movements and relatively large size.”
- Breeding: “As with other members of the genus, this is not a difficult species to breed, being an egg scatterer.”
From the Seriously Fish profile for this species, which has the full habitat, maintenance, diet, behaviour and breeding write-up 167
Rainbowfish
Applies to most species in this group. Habitat: Rainbowfish inhabit Australian and New Guinean freshwaters, including vegetated lake shallows and the slow streams, swamps and billabongs used by threadfins. Individual species can differ, so compare with the species numbers above and the linked sources.
Housing & setup
- For Melanotaenia boesemani, provide at least 120 × 30 × 30 cm (about 48 × 12 × 12 inches) with open swimming lanes.
- For Iriatherina werneri, use a base at least 60 × 30 cm (24 × 12 inches), planted margins and gentle flow.
- Use efficient filtration and maintenance; threadfins require a mature tank with stable chemistry.
- Boeseman’s rainbowfish are sourced at pH 7.0–8.0 and 10–20 dGH; threadfins at pH 5.0–8.0 and 1–12 dGH.
Diet
- Quality dried foods; finely crush floating foods for threadfins.
- Live or frozen foods sized to the fish’s mouth.
- For threadfins: Daphnia, Moina, Artemia nauplii or copepods.
Social life
- Boeseman’s rainbowfish do best in shoals of at least 6–8. Keep threadfins in at least six, preferably ten or more, with small peaceful fish that neither nip fins nor monopolize food.
Health watch
- Ammonia toxicity.
- Nutritional deficiencies.
Understanding the animal
About this animal
About this animal
The southernmost species of all rainbowfishes, these fish are very colourful, hence the name; and there is sexual dimorphism with the males being larger and more colourful than females. Murray River rainbowfish are schooling fish and will congregate near logs or riverbanks, and are a popular aquarium fish.
Quoted from the Wikipedia article “Murray River rainbowfish” (CC BY-SA 4.0) 174
In the wild
In the wild
From this species’ own FishBase record (habitat, bottom type, water and breeding data), not its family. Good care copies these conditions.1
| Where it lives | Lives in freshwater. Uses both the bottom and open water. Found in rivers, creeks, drains, ponds and reservoirs. Occurs usually in still or slow-flowing conditions. |
| Water it lives in | Freshwater, 72–77 °F (22–25 °C), pH 7, hardness 10 dH. |
| Climate | Tropical climate. |
| Behavior to plan for | Breeding: open water/substratum egg scatterers. |
What this means for care
- Keep water within its wild range, 72–77 °F.
Native climate (measured)
Native climate (measured)
| Warm-season highs | about 90°F (up to 95°F in the hottest sampled areas) |
| Cool-season lows | about 40°F (down to 37°F in the coldest sampled areas) |
| Average temperature | 59–69°F across sampled records |
| Relative humidity | 52–62% on average (driest month about 44%) |
| Rainfall | about 531 mm a year, spread fairly evenly |
| Winters | Cool to cold winters (lows around 40°F) in much of its native range. Seasonal slowdown may be relevant, but species-specific biology determines whether brumation or hibernation occurs. |
Measured at 162 wild occurrence records sampled against WorldClim 2.1 climate data (1970–2000 averages). Air conditions in the range are ecological context, not enclosure settings: microhabitats such as burrows, leaf litter or basking rocks can be cooler, warmer or more humid.
From the sources
From the sources
Quoted from the matching sections of reputable sources for this exact species. Specialist databases are used first; Wikipedia (community-edited, CC BY-SA 4.0) only fills gaps. Other sources are short credited quotes.
| Overview | The Murray River rainbowfish (Melanotaenia fluviatilis), known less commonly as the Australian rainbowfish, is a species of freshwater fish endemic to southeastern Australia. The southernmost species of all rainbowfishes, these fish are very colourful, hence the name; and there is sexual dimorphism with the males being larger and more colourful than females. Murray River rainbowfish are schooling fish and will congregate near logs or riverbanks, and are a popular aquarium fish. — Wikipedia (community-edited) |
| Where it lives | Home ranges Population dynamics Growth parameters Max. ages / sizes Length-weight rel. Length-frequencies Mass conversion Recruitment Abundance Life cycle Reproduction Maturity Maturity/Gills rel. — FishBase |
| Behavior | Murray River rainbowfish are omnivorous and feed on both aquatic and terrestrial invertebrates and some filamentous algae. In captivity, their diet comprises all kinds of live foods, as well as flake food. They are peaceful in temperament and tend to school around logs and grassy riverbanks. — Wikipedia (community-edited) |
| Appearance and size | Maximum length 11.0 cm sl male/unsexed. — FishBase |
| Biology | Found in rivers, creeks, drains, ponds and reservoirs. Occurs usually in still or slow-flowing conditions. Inhabits streams, backwaters of larger rivers, drainage ditches, overflow ponds and reservoirs. — FishBase |
| History and naming | Melanotaenia fluviatilis was originally described by François de Laporte de Castelnau as Aristeus fluviatilis. M. fluviatilis was formerly considered a synonym of the closely related crimson-spotted rainbowfish (M. duboulayi). Authors recognised M. duboulayi and M. fluviatilis either as a single species or separate subspecies, or even as two subspecies of eastern rainbowfish (M. splendida). — Wikipedia (community-edited) |
Data and studies
The numbers
The numbers
Each bar is what one source reports. Where several sources weigh in, the dashed gold band marks their average.
Adult length
Common length to maximum recorded length. Measured as standard length (snout to the base of the tail, not counting the tail fin). Fish in home aquariums often stay smaller than wild records.
Water temperature
Range the species tolerates in nature; aim for the middle.
pH
Water hardness
Minimum tank footprint
Seriously Fish recommends a tank base of at least 35 × 12 in (about 21 US gallons).
Sources for this sheet
- FishBase (Froese & Pauly, eds.), version 24.07 Peer-reviewed researchThe global scientific database on fishes, maintained by a consortium of research institutions; every value is referenced.
- Seriously Fish species profiles Experienced keeper or breederLong-running aquarium reference written and peer-checked by experienced fishkeepers and ichthyologists; each profile covers habitat, tank size, water, diet, behaviour and breeding.
- Seriously Fish — Melanotaenia boesemani Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Seriously Fish — Iriatherina werneri Experienced keeper or breederAdded in the 2026 source-checked care-guide review.
- Merck Veterinary Manual — Disorders and Diseases of Fish Zoo, university or veterinaryAdded in the 2026 source-checked care-guide review.
- Wikipedia (species article) Community referenceFree encyclopedia; useful overviews with their own citations. Intro text is quoted under CC BY-SA 4.0.
- iNaturalist (captive observations) Community referenceCommunity observation platform run by the California Academy of Sciences and National Geographic; observations marked captive show animals living in homes, zoos and aquariums.
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