Turquoise Rainbowfish (Melanotaenia lacustris) Care Guide
A stunningly colored rainbowfish with a two-tone blue body — deep cobalt blue on top transitioning to bright turquoise below.
Compiled by Aquairi from published sources · Published · Updated
Overview
Melanotaenia lacustris is a species in the family Melanotaeniidae. A stunningly colored rainbowfish with a two-tone blue body — deep cobalt blue on top transitioning to bright turquoise below. One of the most beautiful rainbowfish species, endemic to Lake Kutubu in Papua New Guinea.
Taxonomy
- Family: Melanotaeniidae
- Genus: Melanotaenia
- Scientific name: Melanotaenia lacustris
- Other names: Lake Kutubu Rainbowfish
- Origin: Oceania, Papua New Guinea
Habitat
Endemic to Lake Kutubu and its outflow into the Soro River, a karst lake at about 800 m elevation in the Southern Highlands Province of Papua New Guinea. Listed as Vulnerable on the IUCN Red List due to introduced species and habitat change.
Tank requirements
- Minimum tank volume: 150 L
- Temperature: 22-26 °C
- pH: 7-8.5
- GH: 10-20 °dGH
- Water flow: moderate
- Adult size: 8-12 cm
- Lifespan: 5-8 years
- Recommended group size: ≥ 6
- Difficulty: beginner
Diet
Classified as omnivore. Recommended feeding frequency: 2x daily. In captivity, offer a varied diet appropriate to the species — quality prepared foods supplemented with frozen or live items of suitable size.
Compatibility
- Temperament: peaceful
- Swimming level: middle
- Compatible tank mates: Boesemani Rainbow, Corydoras, Bristlenose Pleco, Cherry Barb
- Avoid with: Small Nano Fish, Aggressive Cichlids
Breeding
- Breeding strategy: egg-scatterer
- Breeding difficulty: intermediate
Lake Kutubu Rainbowfish Breeding Guide
Overview
Melanotaenia lacustris is a plant-spawning rainbowfish endemic to Lake Kutubu in the Kikori River system of Papua New Guinea, where it is one of 13 endemic fish species. It is a continuous spawner that deposits small batches of adhesive eggs over a period of weeks rather than in a single event, which makes it accessible to intermediate aquarists willing to harvest eggs regularly.
Sexing
Males are larger and more brightly coloured and develop a noticeably deeper body than females as they mature. When ready to spawn, males display to one another almost constantly and develop an orange patch above the gill flaps, while conditioned females become noticeably plumper with eggs.
Conditioning
Condition the adults as a group in a separate aquarium with plenty of live and frozen foods. Heavy feeding brings the females into spawning condition; readiness is indicated by the females filling out and the males displaying intensely to each other.
Breeding Setup
- Spawning tank at least 30 inches (76 cm) long, no substrate needed
- Slightly hard, alkaline water around pH 7.5
- Temperature 72-75°F (22-24°C)
- Small air-powered filter for oxygenation
- Fine-leaved plants such as java moss, or nylon spawning mops as an egg-receiving medium
Spawning Behavior & Trigger
A small rise in temperature often induces spawning. The selected pair spawns over a period of several weeks, laying batches of eggs each day. Eggs are attached to plants or mops by a small thread.
Egg & Fry Care
Adults eat their own spawn, so eggs should be removed regularly to a separate rearing tank. The eggs hatch in 7-12 days depending on temperature. Newly hatched fry stay very close to the surface and require infusoria-type first foods, graduating to free-swimming foods such as brine shrimp nauplii after about a week. Avoid sinking foods, which the surface-oriented fry will not reach.
Common Challenges
The two main difficulties are egg predation by the adults, addressed by daily egg harvesting, and the small mouth size of the surface-dwelling fry, which makes a steady supply of infusoria essential during the first week. This species is also Endangered in the wild, so captive breeding helps relieve collection pressure on the natural Lake Kutubu population.
Turquoise Rainbowfish (Melanotaenia lacustris) Breeding Guide
Overview
Melanotaenia lacustris is endemic to Lake Kutubu and the River Soro in Papua New Guinea and reaches about 12 cm. It is described as not a difficult species to breed, being an egg scatterer onto fine-leaved plants or spawning mops.
Sexing
Mature males are larger and more brightly coloured than females, and develop a much deeper body as they grow. When in condition, males also display an orange patch above the gill flaps.
Conditioning
Bring adults into condition before spawning; conditioned males show the characteristic orange head patch that signals readiness. A varied diet supports egg production over the extended spawning period.
Breeding Setup
Use a spawning tank of at least about 75 cm in length with slightly hard, alkaline water of around pH 7.5 and a temperature of roughly 22-24 °C. Provide fine-leaved plants such as java moss or spawning mops as an egg-laying substrate; no substrate is needed on the base.
Spawning Behavior & Trigger
The pair spawn over a period of several weeks, laying batches of eggs each day. The eggs are attached to surfaces such as the plants or mops by a small thread.
Egg & Fry Care
Eggs hatch in 7-12 days depending on temperature. The fry initially require an infusoria-type food before graduating onto free-swimming foods such as brine shrimp nauplii after a week or so.
Common Challenges
Because eggs are laid continuously over weeks, mops or plants must be checked and rotated regularly so that early eggs are not eaten and fry of similar age can be reared together. Matching the slightly hard, alkaline water the species prefers also supports good hatch rates.