Red Rainbowfish
Glossolepis incisus
The Red Rainbowfish (Glossolepis incisus) is undoubtedly one of the most striking and solid-colored freshwater species. Mature adult males transform into an incredible vision of bright salmon red or iridescent blood red, with scales that look like light-reflecting metallic foils. Famous for its exceptionally high and compressed body profile (humpbacked), it is a tireless and powerful swimmer that, like its cousin Boesemani, needs huge open spaces to exhibit its natural schooling behavior.
Water Temperature
22 - 26 °C
pH Value
7 - 8
Water type
Freshwater
Tank level
Surface and middle
Adult size
15 cm
Minimum tank volume
>= 300 L
Minimum group
>= 6
GH
10 - 20 dGH
KH
5 - 10 dKH
TDS
200 - 400 ppm
Conductivity
313 - 625 uS/cm
Species description
Geographical Origin and Habitat: Endemic only to Lake Sentani in New Guinea (Papua). Lives near the turbid shores of this specific mountain lake, where the waters are hard, alkaline and rich in submerged lacustrine vegetation.
Taxonomy and Morphology: Red Rainbowfish. Corpulent and very high species (lozenge shape). It is the most famous and impressive of the Melanotaeniidae family. It can easily exceed 15 cm (6 inches) in length and 6 cm (2.5 inches) in back height as an adult.
Social Behavior: Extremely gregarious and very lively swimmer. Absolutely must be kept in schools of at least 6-8 specimens with a proportion of more females for each male. Males engage in wonderful color parade exhibitions to establish hierarchies and fascinate females.
Coloration and Sexual Dimorphism: Dramatic sexual dimorphism. Adult males, if well fed, ignite with an incomparable metallic fire red or burgundy color, with small bright silver scales on the body. Females are slender and an anonymous transparent yellow/olive for life.
Care, breeding and tankmates
Aquarium Setup: Tank at least 120-150 cm (4-5 feet) long (minimum 250 liters / 65 gallons) given the lightning-fast swimming. There must be wide open central swimming spaces with lateral thickets of Vallisneria or Cryptocoryne. Does not like excessive light: shade with floating plants (Ceratopteris).
Diet and Feeding: Extremely voracious omnivore that feeds in the upper part of the water column. Flake food and small sinking pellets enriched with astaxanthin (to enhance the red) are the base; frozen bloodworms, daphnia and brine shrimp nauplii are essential to unleash the iridescence.
Water Quality: HARD and alkaline water species: unlike common South American fish, G. incisus suffers and wastes away in soft or acidic waters. Maintain pH at 7.5-8.0 and a GH between 10 and 20. The temperature must be cool, around 23-25°C (73-77°F). Frequent partial water changes.
Compatibility and Cohabitation: Perfect for community tanks of robust and good-sized fish. Splendid companion for other Rainbowfish species (Melanotaenia praecox or boesemani), large Corydoras, Ancistrus. Never pair with small fish (Microrasboras) or shy soft-water fish (Discus).
Aquarium Breeding: They scatter adhesive eggs among the bushes of fine plants (mosses or spawning mops) every morning for weeks. The breeders must be removed or they will devour the clutch. The fry are extremely fragile and tiny, requiring infusoria and rotifers for the first few days.
Risks and Diseases: Old males develop an incredibly curved and stocky back (physiological gibbosity). They are vulnerable to Fish Tuberculosis (Mycobacteriosis) if kept in overcrowded, hot (over 28°C / 82°F) and nitrate-polluted waters.
Geographic Origin and Distribution
Endemic only to Lake Sentani in New Guinea (Papua). Lives near the turbid shores of this specific mountain lake, where the waters are hard, alkaline and rich in submerged lacustrine vegetation.
Origin
Tropical oceans and reefsAfrica and MadagascarSouth and Southeast AsiaEast AsiaAustralia, New Guinea, and Oceania
Fish profile
- Temperament
- Peaceful
- They exhibit a very peaceful demeanor. Males may briefly spar to establish dominance. Overall, they are perfect for community tanks.
- Diet
- Omnivore
- These fish are naturally omnivorous. Provide a high-quality flake or pellet staple. Supplement with live or frozen bloodworms.
- Life expectancy
- 5-8 years
- In captivity, this lively species has an average life expectancy ranging from 5 to 8 years. Proper maintenance with regular water changes is essential to ensure the fish's health and prevent stress. Providing a spacious aquarium and a complete diet significantly reduces the risk of early diseases.
- Adult size
- 15 cm
- The catalog's scalar value is 15 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 12 cm for this species, recorded as standard length (SL). The taxonomic link follows a synonym to the FishBase SPECIES table (v25.04 snapshot) record for Glossolepis incisa (v25.04); male or unsexed record. These figures are not interchangeable: the first is the profile's editorial reference, whereas the second is a published maximum under a specific measurement convention; differences among sources can reflect sex, population, life stage and measuring method.
- Sex ratio
- Specific M:F ratio
- Keep one male for every two females. This ratio minimizes male aggression. A proper group size highlights their best colors.
- Feeding frequency
- Twice daily
- Feed them small portions twice daily. They should finish the food within minutes. Avoid overfeeding to maintain water quality.
- Bioload
- Medium to High
- Red Rainbowfish have a moderate bioload. They process food quickly due to high activity. Efficient filtration easily handles their waste.
- Flow
- Moderate
- They enjoy a moderate to strong water flow. This mimics their natural river environments. Powerheads can help create suitable currents.
- Jump risk
- Yes
- Red Rainbowfish are notorious jumpers. They can easily leap out when startled. A tight-fitting lid is absolutely essential.
- Reproduction
- Oviparous
- They are prolific egg scatterers. Spawning mops or fine plants catch the eggs. Remove parents promptly to prevent egg consumption.
- Compatibility & tankmates
- Verify
- They are peaceful schooling fish. Keep them with similarly sized tank mates. Avoid keeping them with aggressive fin-nippers.
- Tank level
- Top/Middle
- They prefer the middle and upper levels. These fish swim actively in open water. Provide plenty of unobstructed horizontal swimming space.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 2.8 ± 0.3 se
- Resilience
- Medium (1.4 - 4.4 years)
- Phylogenetic uniqueness (PD50)
- 0.502
- Bayesian Length-Weight
- a = 0.01122, b = 3.04
- VulnerabilityLow vulnerability (10 / 100)
Image gallery
Licensed images linked to the species or, when marked, to the closest representative taxon.
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Recommendations grouped by close relatives, companion choices, and similar care.
