Nematobrycon palmeriRainbow tetra

Geographic Range

Nematobrycon palmeri is found in the streams and rivers of Western Colombia in South America (Lundie 2000).


Nematobrycon palmeri lives in pelagic, freshwater rivers of South America. A pH range of 5.0 to 8.0 and dH range of 5.0 to 19.0 can be tolerated by this species. The rivers that contain Emperor tetra are located in tropical regions where the temperature ranges from 23 to 27°C. (Torres 2000)

  • Aquatic Biomes
  • rivers and streams

Physical Description

Nematobrycon palmeri has a body that is about 39 mm deep and laterally compressed. Anterior to the dorsal fin, body profile is partially convex. Posterior to the dorsal fin, the profile again becomes slightly convex until the caudal peduncle, where the body continues parallel to the lengthwise body axis until the procurrent caudal fin rays. The ventral profile is rounded and protrudes the most at the origin of the pelvic fin. The head reaches a length of about 20 mm. Approximately 6 mm of that is the snout. The scales of Nematobrycom palmeri are fairly large. The lateral line slopes slightly ventrally and is incomplete. There are generally 33 lateral scales, with 7 scales above the lateral line and 5 below. There are 14 scales around the caudal peduncle. The dorsal fin is located anterior to the anal fin, and posterior to the insertion of the pelvic fin. In males, the third ray of the dorsal fin is the longest, whereas the fourth or fifth is longest in females. The origin of the anal fin is located just behind the midpoint of the body. The pectoral fin is low on the body, either rounded or pointed, and is located about 28 mm from the snout. The pelvic fin is about 19 mm long and is found approximately 44 mm from the tip of the snout. The males of this species have a moderately wide black stripe that spans the length of the body, from the jaws to the posterior tips of the middle caudal rays. The scales above the stripe are a greenish blue color, with a narrow orange-yellow brown stripe that extends horizontally from the midpoint of the body to the caudal fin origin. This stripe is located just above the thick black stripe. The top of the head and back are a dark brown color. The scales just below the black strip are a pale tan. The belly of this species, as well as the underneath of the head, is white. The iris is specular blue as well as the area of the head just behind the eye. The fins are hyaline in color. The first three or four rays of the dorsal fin are black. The upper and lower edges of the caudal fin are also black. The central elongate rays of the caudal fin are black (continuing the black side stripe). Some of the rays of the fins are a creamy white color. The females have the same coloration, except they lack much of the specular blue (just a thin stripe above the lateral black stripe), much of the black on the rays of the fins, and almost all of the creamy white on the fins. There is also a black from of this species. (Weitzman & Fink 1971)


Nematobrycom palmeri is dioecious, meaning there are male reproductive organs in one individual and female reproductive organs in another. Fertilization is external and occurs in open water. Only one egg is laid at a time, so spawning takes several hours. The parents do not stay and guard their eggs, but they may eat them. (Lundie 2000, Torres 2000)


This fish is very peaceful in temperment - one of the reasons for its popularity in the aquarium trade (Lundie 2000). Groups of this species participate in schooling behavior. This activity increases an idividual's safety, as predators observing the group would only see splashes of specular blue from the scales on the sides of each fish. (Fink 2000)

Communication and Perception

Food Habits

Nematobrycon palmeri is omnivorous in the wild, consuming worms, crustaceans, and plant material. In one year, this species consumes approximately 60 times its body weight. No information was found on the methods of feeding implemented by this fish.

(Lundie 2000, Torres 2000)

Economic Importance for Humans: Positive

This species is very popular in the aquarium trade in the United States. A black form of Nematobrycon palmeri is very common in aquariums as well.

Economic Importance for Humans: Negative

There is no negative economic impact on humans caused by Nematobrycon palmeri.

Conservation Status

This species does not have an IUCN threatened status (Torres 2000).


William Fink (editor), University of Michigan-Ann Arbor.

Jonathan Marceau (author), University of Michigan-Ann Arbor.



living in the southern part of the New World. In other words, Central and South America.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.


uses smells or other chemicals to communicate


having the capacity to move from one place to another.


specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.


uses touch to communicate


Castro, A. 2000. "Ten Steps to Breeding Tetras" (On-line). Accessed October 30, 2000 at

Fink, W. 11/7/2000. "Some of these small fishes are among the "butterflies" of the rainforest pools and streams." (On-line). Accessed November 14, 2000 at

Lundie, A. 2000. "Exotic Tropical Fish - Emperor Tetra" (On-line). Accessed October 30, 2000 at

Torres, A. 2000. "Species Summary for Nematobrycon palmeri" (On-line). Accessed November 14, 2000 at

Weitzman, S., W. Fink. 1971. A new species of characid fish of the genus Nematobrycon from the Rio Calima of Columbia (Pisces, Characoidei, Characidae). Beaufortia, 19(248): 57-77.