Emperor Tetra (Nematobrycon palmeri)

Nematobrycon palmeri, also known as the Emperor Tetra, is a characid fish (freshwater subtropical and tropical fish) found in slow running parts of rivers, minor tributaries, and blackwaters in western Colombia (Atrato and San Juan) with sandy, rocky or muddy bottoms. They live up to 5 years and in good tank conditions, they can live even more.



Nematobrycon palmeri has an impressive and elegant appearance. They have slimmer bodies with their adult size being between 3 and 5.1 cm (1.2 – 2 inches). The males are more colorful and slightly larger than the females with a taller body and a longer fin. Their overall color hue is purple blended with yellow and an olive-brown on the back. If the tank has dim lighting, their purple hue will be more apparent and on the other hand, if the light is too bright, their yellow hue will dominate. They have a median black line placed within a blue stripe starting from the eye and ending at their tail. In males, the black line will extend on the three-pronged tail and will appear like a crown. The females do not have a three-pronged tail in general. But, sometimes dominant females may grow this extension.


The eye color differs between sexes. While the eye color is metallic blue in males, females have metallic green eyes. They are often confused with N. lacortei, but they can easily be told apart by comparing their eyes – N. lacortei has a bright red iris while Nematobrycon palmeri has green and blue eyes.

Behavior and Compatibility

N. palmeri is a lively, peaceful, and shy fish. They are one of the best tetra species for the community setups. It’s a shoaling, social species by nature and it is better to keep this species in groups of 6, 10, or more.
They make a good tankmate and can be kept without problems with the following species:

  • Dwarf cichlids such as German blue rams, Kribensis cichlids, Bolivian rams,
  • Rasboras,
  • Gouramis,
  • Peaceful bottom dwellers like Corydoras catfish and Loricariids,
  • Livebearers (Guppies and platies),
  • Zebra danios,
  • Pencil fish
  • Apistogramma
  • And most species of peaceful tetras.
    It is not recommended to be kept with bigger and over-active species because N. palmeri can often be seen as food or prey.

Some males will tend to become territorial, but their battles will not result in serious damage, therefore it’s preferable to keep only one male in a tank but not mandatory.

Water Parameters

Temperature: 23-28°C
pH: 5,0 – 8,5
Hardness: 5 – 19 dGH

Emperor Tetras are unfussy and adaptable freshwater fish. It is recommended to provide soft and acidic water for them to be in the best health and condition.

Proper Tank Conditions

The provided tank should be sufficiently large (minimum 57 liters) and well-decorated (plenty of ornaments, driftwoods, and live plants) with a rocky (gravel) or sandy substrate.

If there is more than one male in the tank and they are territorial, the driftwoods will help them break their line of sight and reduce aggression by providing them separate territories.

A lot of plants (Water Sprite or Java moss) and soft lighting will mimic their natural habitat in the rivers of Columbia.

When it comes to filtration, it is better to use a filter that has a water flow between 4-5 times the volume of your tank to sufficiently filter the water and provide some flow.


Nematobrycon palmeri is omnivorous fish and they are not picky eaters. In the wild, they eat insect or fish larvae, small insects, and invertebrates.

In the aquarium, they will eat live and frozen food (mosquito larvae, daphnia, bloodworms, tubifex, and brine shrimps), pellets, and flakes suitable for their small mouths. To maintain their beautiful colors, feeding them with high-quality fish foods alternated with live or frozen foods is substantial.

Feeding them once or twice a day with small portions that won’t let any uneaten food remain in the tank is the best feeding method. It will also keep the water quality high.

In a large, well-planted aquarium the free-swimming fry would feed with the protozoa and algae that naturally grow in the aquarium. After about a week they can be fed with baby brine shrimp or microworms and powdered flake foods.


Nematobrycon palmeri is not a difficult species to breed because they don’t need any special stimulation. Only a well-planted aquarium (Water Sprite, Java moss, or spawning mops) for giving them a place to deposit eggs provides the proper breeding conditions. Also, enough hiding space for the fry with dim lighting and acidic water is all they need to breed in a species only aquarium.

Another option is to cover the bottom of the tank with a mesh that has proper-sized holes for the eggs to fall through, but also small enough to hinder the adults will ensure breeding.

It is recommended to have an equal number of males and females for breeding and also a large separated tank to provide males the space they need if they become territorial. The separated males and females should have a live food diet for at least a week to get well-conditioned before breeding.

When the females are full of eggs the males will start displaying their colors. Once they lay the eggs, they can be removed for preventing them to eat the eggs. The eggs will hatch in 24-36 hours and the fry will become free swimming in 4-6 days.

If the eggs/fry are kept in the same aquarium with the adults in a species-only well-planted tank and also, if the adults are well-fed, some of the babies may survive.

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