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Glowlight Tetra

Hemigrammus erythrozonus


Hemigrammus erythrozonus - Glowlight Tetra

Glowlight Tetra

Essequibo River

Essequibo River

Hemigrammus erythrozonus - Glowlight Tetra

Glowlight Tetra

  • Scientific Name: Hemigrammus erythrozonus
  • Synonym: none
  • Common Names: Glowlight Tetra, Glolight, Fire Neon
  • Family: Characidae
  • Origin: Essiquibo River, Guyana
  • Adult Size: 1.5 inches (4 cm)
  • Social: Peaceful, schooling
  • Lifespan: 5 years
  • Tank Level: Mid
  • Minimum Tank Size: 10 gallons
  • Diet: Omnivore, needs small foods
  • Breeding: Egg scatterer
  • Care: Easy
  • pH: 5.8–7.5
  • Hardness: up to 15 dGH
  • Temperature: 74-82 F (24-28 C)



The Glowlight Tetra originates from the the Essequibo basin in Guyana, having been found in the Essequibo, Mazaruni and Potaro Rivers. Areas of these waters are stained with tannins, making them naturally soft and acidic, conditions that the Glowlight Tetra thrives in. Originally exported for the aquarium trade in 1933, the Glowlight Tetra is also bred in, and exported from, Asia and Germany. Originally assigned the name Hemigrammus gracilis, it was later changed to the current name of Hemigrammus erythrozonus. However, scientists continue to study this fish and it may ultimately be moved to the genus Cheirodon.


Peaceful and easy to care for, the Glowlight Tetra is one of the most popular of all Tetras. Small and slender, they reach an adult size of only an inch and a half in length. The translucent silvery-peach colored body of the Glowlight Tetra is divided by an iridescent red-gold stripe running from snout to tail. The stripe resembles the glowing filament in a light bulb, hence the common name of Glowlight. The same iridescent red color is present on the leading edge the dorsal fin, while the anal and pelvic fins are edged in snow white.

The trademark stripe of the Glowlight Tetra is shared by a species of Rasbora, known as the Red-line or Glowlight Rasbora, and the two fish are sometimes confused. However, the two species are not from the same Genus. The most obvious difference between the two is the lack of an adipose fin in the Rasbora.


Glowlight Tetras are schooling fish that should always be kept in groups of at least a half dozen or more. They may be kept with other small peaaceful fish, including other small Tetras, Barbs, Danios, Cory Catfish, and peaceful Loaches. Although they are a schooling fish, they will generally not school together with other species. This is true even with species of similar size and shape, such as the Neon and Cardinal Tetras. Slow moving fish, and fish with long fins, are safe with Glowlight Tetras. However, avoid Angelfish as they will consider the Glowlights tasty snacks, and eat them. Avoid all large fish, as well as any fish that are predatory. Fish that are extremely active make prove stressful for the Glowlight Tetra.


Glowlight Tetras are most attractive, as well as most comfortable, when kept in a darkened tank. Chose dark susbstrake and provide plenty of vegetation, but leave some open space for swimming. Added tannins to both soften and darken the water, combined with floating plants, will provide the finishing touch to the perfect Glowlight Tetra habitat. The water should be soft and slightly acidic, with a hardness of 6 to 15 dGH, and pH of about 6.6. They prefer warmer water temperature in the upper 70s. Glowlight Tetras tolerate a wider range of water parameters than similar species, such as the Neon and Cardinal Tetras.


Glowlights are omnivorous, meaning they will eat all types of foods. The important factor is to feed small sized foods, and vary the diet. Live foods are readily accepted, as are flake, freeze-dried, and frozen foods. They will rarely eat food that has fallen to the bottom, so it is advisable to feed small quantities more frequently, as opposed to less frequent large feedings. Micro pellet foods are suitable, as well as any good quality flake that has been crumbled into fine pieces. Brine shrimp is readily accepted, either frozen or fresh.

Sexual Differences

Female Glowlights are larger bodied and plumper than males. The males are generally smaller and more slender, particularly in the abdomen, which is more rounded in the female.


Glowlight Tetras have been successfully bred in the aquarium, but are known to be somewhat challenging in that regard. A separate breeding tank should be prepared with very soft water of no more than 6 dGH and pH of 5.5 to 7.0. The use of peat to soften and darken the water is recommended. Water temperature should be warm, in the range of 78 to 82 F (26-28 C). The tank should have very low lighting, ideally only light from the room the tank is in. Plant the tank with fine-leafed plants, such as Java Moss. A spawning mop is also suitable in lieu of moss.

Condition the fish with three to five small feedings per day. Vary the diet, including live foods if possible. When a female becomes very plump, place her and a male in the breeding tank. When the pair is ready to spawn, the male will dart about the tank after the female, ultimately performing a courtship display in which he flicks his fins and shimmies near the female. After a time this courtship culminates in both fish rolling on their backs, the female ejecting her eggs, and the male fertilizing them. A typical spawning will produce between 100 and 150 eggs. The parents provide no parental care, and will eat the eggs if they get the opportunity. Therefore they should be removed as soon as spawning is complete. Some breeders favor placing a spawning grate on the bottom to protect eggs that fall to the bottom.

The eggs are extremely light sensitive, and it is recommended that the rearing tank be kept dark. Hatching occurs in approximately one day, and the fry become free swimming in three days. At two weeks of age, the fry show silver coloration, and at three weeks they begin to show the trademark glowing line through the middle of the body. Initially the fry can be fed with infusoria or paramecium cultures, finely crushed flake food. Within a few days they may be fed freshly hatched brine shrimp. Microworms may be added to their diet once they grow a bit larger.

Readers Respond: Have you kept a Glowlight Tetra?

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