At a glance the quick version
Standard length: FishBase gives 10 cm, Seriously Fish 12 cm
Looks how to spot one
Scaled, laterally compressed rainbowfish
A torpedo-shaped fish when young; adult males grow much deeper in the body than females and become the brightest of the pair. Breeding males show an orange patch just above the gill covers. Young fish in shops look fairly plain and take a year or more to reach full adult colour.1
Personality what they are like
A peaceful, busy schooling fish that gets along with most similar-sized tankmates, though its energy can unsettle very small or slow fish.12
Daily activity how busy a day looks
An active open-water swimmer that needs a long tank with clear swimming lanes alongside planted areas.1
Grooming and care the hands-on bits
Plant the tank well and keep the water flow gentle. Be patient with juveniles: the full adult colour can take over 12 months to appear.1
Home where they are happiest
Minimum tank about 120 x 30 x 30 cm (around 108 litres). Temperature 20-25 °C, pH 7.0-9.0 (FishBase gives 7.0-8.0), hardness roughly 9-20 dGH. A planted layout with rocks and driftwood suits it.12
Food basics what goes in the bowl
Omnivore. Accepts dried, frozen and live foods; a varied diet keeps it in good colour.12
Company who they like around
Keep a group of at least 6-8; larger shoals look and behave best.1
The story where it all began
Munro described the species in 1964 from Lake Kutubu, a highland lake in Papua New Guinea that formed when volcanic debris dammed a valley. It has since become an established aquarium fish and is bred commercially for the hobby.213
Fun facts for the dinner table
- 1
It lives naturally in only one lake and its outflow river, and nowhere else in the world.3
- 2
Lake Kutubu has many fish found only there; Seriously Fish counts 10 of its 14 native species as endemic.1
- 3
Juveniles are often sold as plain 'blue' rainbowfish and only reveal their full turquoise sheen after about a year.1
- 4
Pairs show distinct pairing behaviour when spawning.2
Recognised by the official bits
- IUCN Red List
- Endangered (assessed December 2019); an older listing cited by Seriously Fish gives Vulnerable2
- Taxonomy
- Family Melanotaeniidae; described by Munro in 19642
The care rhythm Furry Diary remembers it for you
A typical home-care rhythm for a Turquoise Rainbowfish. It is our own starting plan, not a vet's advice, and you can change every line in the app.
- FeedingSmall amounts once or twice a dayevery day
- Temperature checkevery day
- Water changeAbout 25% of the waterevery week
- Water testevery week
- Glass cleanevery week
- Filter rinseRinse in old tank water, never tap waterevery month
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Where this comes from
Every breed page shows where each fact comes from. If we got something wrong, sorry, we are pet people, not a science magazine. Tell us at [email protected] and we will fix it.
- Seriously Fish: Melanotaenia lacustris (Lake Kutubu Rainbowfish) seriouslyfish.comused for habitat, size, tank size, water parameters, diet, group size, dimorphism, colour development, endemism
- FishBase: Melanotaenia lacustris, Lake Kutubu rainbowfish fishbase.seused for author and year, distribution, max length, water ranges, IUCN status, behaviour
- Wikipedia: Lake Kutubu rainbowfish en.wikipedia.orgused for other names, endemism, IUCN status
Checked 2026-09-30. Text is written in our own words from these sources.