Emperor Tetra (Nematobrycon Palmeri) – Care Guide, Behavior and Breeding

emperor tetra

The Emperor Tetra is an underappreciated freshwater fish that we have long admired. While they aren’t as well-known as some of the other tetras, we believe they deserve greater attention. These fish have a subtle elegance that shows through when you see them in person.

Not only that, but they are also incredibly simple to maintain! This tutorial will teach you the fundamentals of Emperor Tetra care as well as a wealth of other information that you should be aware of if you are considering becoming an owner. You’ll be eager to purchase some by the time you finish reading it!



The emperor tetra is a simple to care for, resilient, and generally long-lived species for its size. It also has a beautifully calm demeanor, making it perfect for pairing with others. The emperor tetra is an excellent addition to any tank, whether it is a single species or a community tank. This species, which is beautiful, hardy, and affordable, can be found in most dealers’ tanks and is one of the finest choices for the novice to fishkeeping. Because almost all of the fish sold in the trade have been captivity bred, they are often unconcerned with water chemistry and nutrition.

It is occasionally mistaken with N. lacortei, the only other species in the genus. They are easily distinguished by glancing at the eye of the fish in question, since male N. lacortei has a brilliant red iris as opposed to male N. palmeri’s blue iris. Inpaichthys kerri, often known as the ‘blue’ or ‘purple emperor tetra,’ is sometimes mistaken as N. palmeri. This species not only belongs to a distinct (monotypic) genus, but it also grows to a much smaller size and lacks fin extensions. Inpaichthys also has an adipose fin, which Nematobrycon lacks.
In recent years, there has been speculation about the possibility of a third Nematobrycon species, N. “amphiloxus,” which has a much higher proportion of dark patterning on the body and is sometimes sold as a “black emperor tetra.” Most scientists now believe it is a color morph of N. palmeri.

The fundamentals

  • Tank Size: Minimum tank capacity is 10 gallons.
  • Group Size: Bonded couples or a small school of 5 or 6 with one male
  • Water Temperature: Water temperature ranges from 73 to 81 degrees Fahrenheit (23 to 27 degrees Celsius).
  • Life Expectancy: 6 years
  • Breeding: laying eggs
  • Adult Size: 2 in (5 cm)
  • Typical location in the tank: middle to upper levels
  • pH range: 5.0 to 7.8
  • Water Hardness: 3–8 dKH

Emperor Tetra (Nematobrycon palmeri) image

Source: https://web.archive.org/web/20160731154006if_/https://www.petshop-zoomania.com/Tetras,Rainbows,Killi/Nematobrycon%20Palmeri%20male.jpg


The emperor tetra, Nematobrycon palmeri, is a species of characid fish found in the Atrato and San Juan river basins in western Colombia. It was initially introduced to the United States in the aquarium trade in 1960 and has since become well established. Mervyn George Palmer (1882-1954), an English adventurer who collected throughout Central and South America for the British Museum and collected the type specimen, was honored.


The emperor tetra is distinguished by a broad, black longitudinal stripe that runs from the front border of the gill cover to the caudal fin. Males are distinguished by an enlarged dorsal fin and a longer central ray of the anal fin. The male iris is brilliant blue, but the female iris is more greenish. Males who are ready to mate have a vibrant purple belly.
The Emperor tetra’s most notable traits are:

  • The emperor tetra’s (Nematobrycon palmeri) body flanks are a dazzling blue hue. This blue tint might deepen depending on the emperor tetra’s health
  • Below its lateral line is a black longitudinal ligament that extends from the back edge of the gill cover to the base of the tail
  • The male’s Iris glows blue, the female’s green
  • The male’s colors intensify extremely strongly during the mating season: his belly glows purple and his fins are patterned with rich contrasts
  • The male is somewhat bigger than the female and has a larger dorsal and anal fin
  • The emperor tetra’s dorsal and anal fins are well developed, but it lacks an adipose fin
  • The color of its fins is yellowish to brownish.

The purple coloration of these tetras will be more visible in an aquarium with floating plants on the surface and low lighting. If the aquarium is very bright, the yellow hue will take over. At maturity, the body is long, slender, and flattened to around 3 inches. Looking from the eye to the tail, you’ll notice a black line within a blue stripe. The sickled-shaped dorsal fin, as well as the pectoral and anal fins, are all yellow. The male is bigger than the female and has longer anal fins. The male caudal is sharper than the female.
Because Emperor tetras are very sexually dimorphic, men and females may be easily identified. There are numerous methods to tell a male and female different, but the most accurate approach is to look at the color of their eyes. Males have metallic blue eyes, whilst females have metallic green eyes. In addition, the male has a three-pronged tail, with the medial black stripe usually reaching beyond the remainder of the tail, whereas the female’s median black stripe normally only reaches as far as the transparent portion of the tail. However, this is not necessarily the greatest predictor because the third prong in males can be nipped off in contests with tank mates, and more powerful females may also grow this extension of the tail.

Temperament and behavior

Emperor Tetras are naturally peaceful and get along with most non-aggressive fish.
They prefer to dwell around the middle and top of the water column. They may, however, go to the bottom from time to time.
Aggression is uncommon in this species, but when it does occur, it is generally in males. In smaller tanks, males prefer to battle for supremacy.
Typically, this fighting does not result in serious physical injury, but it is still critical to keep a watch on the fish and separate any aggressors.


With appropriate care, an Emperor Tetra may live for around six years.
The lifetime of an Emperor Tetra, like that of any other fish species, is directly impacted by the quality of care they get. Fish housed in poor water conditions are more vulnerable to stress and disease, so it’s critical to pay attention to their requirements and give the finest care possible.
It’s also a good idea to get your fish from a trustworthy seller. This reduces the likelihood of you purchasing a fish with underlying health concerns or genetic abnormalities.

How to take care of for Emperor Tetras

One of the primary reasons Emperor Tetras are so popular among aquarists is their ease of care.
This means they’re not only lovely, but also low-maintenance. These fish are tough and typically undemanding in terms of diet.
Emperor Tetras are tropical species that thrive in freshwater environments. But it doesn’t imply you should take their care carelessly! Here are some well-established care tips to keep your fish healthy.


In nature, it is most likely a micropredator that feeds on tiny insects, worms, crustaceans, and other zooplankton. It will eat dry meals of appropriate size in the aquarium but should not be fed primarily. Daily feedings of tiny live and frozen fish such as Daphnia, Artemia, and the like will result in the best coloration and encourage the fish to reproduce.
The emperor tetra is an omnivore, meaning it eats both animal and plant food. Any decent flake or pelleted fish food can be used as a foundation for its diet. It will benefit from both live food, such as daphnia and mosquito larvae, and frozen fish food, such as frozen bloodworms.

emperor tetra fish


What Should You Put in Their Tank?

If you were to travel to South America and look at the Emperor Tetra’s native environment, you would observe that the waters are dark and densely forested.
Because of these environmental factors, these fish require dim illumination with plenty of hiding spots.
Begin with a dark-colored substrate on the tank’s bottom. You may make use of gravel. Dark-colored sand, on the other hand, is more similar to what is seen in natural riverbeds.
Incorporate live plants into the tank’s design. These plants will serve as hiding places, places to explore, and places to seek refuge from the sun. Floating plants with a lot of leaves can be added. Java fern and water sprite are both wonderful choices.
Plants should be placed all around the tank. However, make sure there is still enough area for the fish to swim around without being entangled in the leaves.
Decorations can be applied on top of the substrate. Driftwood, rocks, and even plastic tank decorations can be used.
A low-powered light and an appropriate filter are required for tank equipment. A dependable hang-on-back filtering system should suffice.

However, you must ensure that the filter’s water output does not create an excessive amount of flow. If required, position plants or decorations to reduce water disruption.
Emperor Tetras thrive in groups of five or six fish. Because of the aforementioned male aggressiveness, it is best to retain only one male in the group. This prevents any conflict and maintains peace in the neighborhood.

Some tankmates to consider

If you don’t want to keep a huge group, these fish may also be kept as a single bonded couple.
There are several more fish species to consider as tank mates. Any comparable sized calm fish will suffice for the most part.
Ideally, you’ll want to keep tankmates from South America who have comparable habitat requirements. It is also critical to avoid bigger fish that may confuse the Emperor Tetra for food. Here are some tank mates to think about:

  • Pencil fish
  • Honey Gourami
  • Celestial Pearl Danio
  • Pearl Gourami
  • Cory Catfish
  • Ember Tetra
  • Sparkling Gourami
  • Apistogramma
  • Guppies
  • Dwarf Gourami
  • Serpae Tetra


If the fish are kept in an ideal habitat, they will typically breed without any assistance. However, you can also initiate the procedure.
You’ll need to set up a separate breeding tank for this. Temperatures in the tank should be approximately 80 to 82 degrees Fahrenheit. The water should be gentle and have a pH balance of about 7.0. To protect the young fish, use a sponge-equipped filter. Fill the breeding tank with a variety of plants. They will play an essential function in protecting the eggs. Because Emperor Tetras are known to devour eggs, the plants will conceal them. You can use a breeding mop instead of plants if you don’t want to use plants.
Separate your bonded couple about a week before you want to start reproducing. Feed the fish live food while keeping an eye on the female. She should start to fill up with eggs soon. When this occurs, place the couple in the breeding tank. Breeding should take place within a day. Over the course of many hours, the female will lay between 50 and 100 eggs. Remove the couple from the breeding tank once she is finished.

The eggs will hatch in two or three days. The newborn fish will live on the egg sack for the first week or so. You may feed them infusoria once they are free swimming. They’ll be ready for powered fish fry meal or baby brine shrimp in about a week. The emperor tetra generally only lays one egg between plants and consumes it right away. As a result, breeding this fish is not especially fruitful. Emperor tetra are free spawners that spawn just below the water’s surface following a period of rapid drifting. Depending on the temperature of the water, the fish larvae hatch in 24 to 36 hours. Emperor tetras, like other free spawners, leave their eggs to chance. After 36 hours, the fish larvae hatch. For the first few days, they can be fed powdered food, followed by newly hatched artemia. A single pair of emperor tetras will frequently reproduce in a large, well-planted aquarium without any further stimulus. If no other fish are around, some of the young may survive, especially if the parents are properly nourished. Protozoa, algae, and other natural foods will be available to the infants in a big, well-planted aquarium. As they develop, screened daphnia will give additional nutrition, and dry fry food can be utilized.
Within the aquarium The emperor tetra is a peaceful aquarium fish that will be bothered by more noisy species. It may reach a height of 4.2 cm. [2] It prefers a pH of 6.5, a hardness of 3-6 dKH, and temperatures ranging from 23–27 °C. It does not school as well as most tetras, and a pair looks to be happier than most tetras. A big number of emperors may school throughout an aquarium, sometimes for many minutes, if fresh chilly water is added.

Diseases common in tetras

Tuberculosis in fish
The Fish Tuberculosis is a bacterial illness that mostly affects tank fish. It is prevalent and causes significant losses.

Foot or fin rot (Columnaris disease)
Milky white patches (mold-like) appear on the fins, the margins of the scales, and the region around the fish’s mouth.

Neon disease (actual) infestations mostly affect neon fish such as the blue neon, neon tetra, and other tetra species such as the redhead tetra, as well as danios such as the zebrafish or ruby barb.

Neon disease (false)
Neon tetra (Paracheirodon innesi, Paracheirodon simulans) and red neon (which is not affected by the “genuine” neon sickness) are potential victims of the fake neon disease (mycosis)

A fungal illness (mycosis)
or infection is always the result of a secondary infection. Fungal infections are sometimes known as “fish mold” or “water mold.”

The velvet disease
When there is a heavy infestation, the skin appears “velvety,” hence the term “Velvet sickness.” This velvety coating is typically golden-yellowish in hue.

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