Emperor Tetra
Nematobrycon palmeri
Majestic Colombian tetra. The male is a territorial 'king' with glowing blue eyes and a unique trident-shaped tail. Hardy and adaptable, but requires a heavily planted tank to disperse male aggression.
Water Temperature
23 - 27 °C
pH Value
6 - 7.5
Water type
Freshwater
Tank level
Bottom and middle
Adult size
5 cm
Minimum tank volume
>= 60 L
Minimum group
>= 6
GH
4 - 15 dGH
KH
2 - 7 dKH
TDS
80 - 295 ppm
Conductivity
125 - 461 uS/cm
Species description
Geographical Origin and Habitat: Western Colombia (San Juan and Atrato river basin). Shares the same habitat as the Amphiloxus: slow secondary jungle streams.
Taxonomy and Morphology: Emperor Tetra (Nematobrycon palmeri). Solidly built Tetra, almost horizontal dorsal profile and curved belly (profile of an inverted knife). No dorsal adipose fin.
Social Behavior: In juvenile age it forms schools; as adults, males develop marked territoriality. They position themselves 20-30 cm (8-12 inches) from each other to show off their fins, dancing upside down as a threat.
Coloration and Sexual Dimorphism: Royal Livery: dark central line edged with cream and an iridescent lavender/light blue back. The male is a masterpiece: bright neon blue eyes and the central spine of the tail elongates into a very elegant "skewer" (Caudal trident). The female has green-yellow eyes and a rounded tail.
Care, breeding and tankmates
Aquarium Setup: 80 cm (32 inches) tank. Shade is fundamental: woods loaded with Epiphytes (Bolbitis, Microsorum), floating lenses (Limnobium) and dark substrate. A Palmeri under intense white LED lights will fade becoming invisible.
Diet and Feeding: Totally undemanding, but being a characin, requires high protein levels. Administer freeze-dried bloodworms, live Brine Shrimp (which it hunts fiercely) and sinking flakes/granules (does not eat on the surface).
Water Quality: Rustic. Among the easiest Tetras to manage regarding chemistry. Excellent at neutral pH (7.0) and comfortably accepts treated tap water.
Compatibility and Cohabitation: Males ignore each other (if there is space) but can persecute very slow fish (male Guppies) mistaking them for territorial rivals. Excellent with Apistogramma and large characins.
Aquarium Breeding: Quite accessible. They spawn early in the morning in roots or moss. If the parents are well fed, a few fry will manage to escape them and grow undisturbed in the crevices of the mother tank.
Risks and Diseases: Tuberculosis from overcrowding. If crammed (e.g. 20 specimens in 60 cm / 24 inches), territorial stress will cause immunodeficiency, leading them to die one by one from Mycobacterium (progressive wasting).
Geographic Origin and Distribution
Western Colombia (San Juan and Atrato river basin). Shares the same habitat as the Amphiloxus: slow secondary jungle streams.
Origin
Extra-Amazon South America
Fish profile
- Temperament
- Semi-aggressive
- They are generally peaceful but males will playfully spar with one another to establish dominance. These harmless displays involve flaring their fins and swimming side-by-side. To feel secure and display properly, they must be kept in groups of at least six individuals.
- Diet
- Omnivore
- This species is an omnivorous micro-predator that accepts almost all aquarium foods. A high-quality flake or pellet should be the core of their diet. Supplementing heavily with live or frozen daphnia, bloodworms, and brine shrimp promotes optimal coloration and breeding condition.
- Life expectancy
- 5-6 years
- In a well-maintained home aquarium, the Emperor Tetra typically has a lifespan of 5 to 6 years under optimal care. Achieving this longevity requires stable water parameters, a stress-free environment, and a high-quality diet. Providing plenty of hiding spaces among live plants also contributes to their general well-being and reduces territorial stress among males.
- Adult size
- 5 cm
- The catalog's scalar value is 5 cm. The FishBase SPECIES table (v25.04 snapshot) source reports a maximum adult measurement of 4.2 cm for this species, recorded as standard length (SL). The taxonomic record consulted is Nematobrycon palmeri (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
- Males possess stunning elongated dorsal and caudal fins and brilliant blue eyes. Females are slightly plumper, less colorful, and have green eyes. Keeping a ratio of two or three females per male prevents the male from harassing a single female to exhaustion.
- Feeding frequency
- Twice daily
- Feeding them small amounts twice daily will keep them healthy and active. Their robust appetites mean they will aggressively outcompete shyer fish for food during feeding time. Ensure that enough food scatters for all fish to receive their share.
- Bioload
- The Emperor Tetra produces a moderate bioload that is easily managed in established aquariums. They are slightly larger than typical tetras, requiring adequate filtration and routine water changes. In heavily planted tanks, the biological impact of a school is extremely manageable.
- Flow
- Stagnant
- They prefer slow to moderate water movement, typical of their native Colombian streams. Extremely strong currents will tire them out and hinder their natural display behaviors. Mild surface agitation provided by a sponge filter or lowered power filter is ideal.
- Reproduction
- Oviparous
- They are relatively easy to breed in captivity compared to other tetras. They are egg scatterers that require soft, acidic water and fine-leaved plants like Java moss for spawning. The adults offer zero parental care and will consume the eggs if not removed.
- Compatibility & tankmates
- They are a superb community fish that mixes well with other peaceful species. Appropriate tankmates include Corydoras, peaceful dwarf cichlids, and other medium-sized tetras. Avoid keeping them with known fin-nippers, as the long fins of the males are tempting targets.
- Tank level
- Middle/Bottom
- They actively utilize the middle levels of the aquarium water column. They will frequently dart into thick vegetation to establish temporary territories or seek shelter. Providing plenty of open swimming space alongside dense planting is the perfect arrangement.
Scientific Parameters & Models
FishBase
Window to the official scientific data of the species
Data synced on: 06/15/2026
- Trophic level
- 3.2 ± 0.36 se
- Resilience
- High (less than 15 months)
- Phylogenetic uniqueness (PD50)
- 0.75
- 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.
Related species
Recommendations grouped by close relatives, companion choices, and similar care.
