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Glowlight Tetra – Hemigrammus erythrozonus


Glowlight Tetra

Tetras are amongst the most popular aquarium fishes. There are probably more than 150 distinct species of tetra from which the aquarist may choose and this includes a large number of visually stunning fishes that are bound to enhance any home aquarium.

Is the Glowlight Tetra a good community fish? The Glowlight Tetra should be considered to be an excellent community fish because it can live quite happily amongst a wide variety of other species. It is best to avoid keeping Glowlight Tetras with large, aggressive species which may bully or even eat the Glowlight Tetra.

Key Facts

CategoryKey Facts
Common name(s)Glowlight Tetra
Scientific nameHemigrammus erythrozonus
FamilyCharacidae
Originate fromEssequibo River, Guyana, South America
Care requiredEasy to care for and hugely popular
TemperamentPlacid, shoaling fish
Colour & FormIridescent orang/red stripe runnung from nose to adipose fin and along the leading edge of the dorsal fin
LifespanUp to 4 years
Adult size1.6 to 2.0 inches
DietOmnivorous – eat aquatic insect larvae in nature
Aquarium size24 inches in length or greater
Compatible withMost other Tetras, Barbs, Danios, Guppies and other livebearers, dwarf cichlids, smaller Gouramis, catfish and loaches
Avoid keeping withLarge and/or aggressive species – especially Angel Fish
BreedingEasy if you put the fish in the right environment.
Adults spawn every two weeks.
Water temp75 – 82 Fahrenheit
Water pH5.0 to 7.5
Water hardness (dGH or dH)1 to 12 dGH

Origins of the Glowlight Tetra

Glowlight Tetras

Tetras, as a “family” of fishes belonging to the biological family Characidae are found in nature in Africa, Central America and South America.

The Glowlight Tetra originates from the Essequibo River, Guyana, South America. As with many tropical fish, the Glowlight Tetra has also been introduced far and wide into different continents that have an appropriate climate.

The Glowlight Tetra is larger than the Neon Tetra and, whilst it is a shoaling fish it tends not to shoal with Neon Tetras but may well shoal with Cardinal Tetras.

Characteristics of the Glowlight Tetra

As you can see, the Glowlight Tetra is a beautiful, little fish which will grow to between 1.6 inches and 2.0 inches in size and live for up to four years. The Glowlight Tetra is omnivorous though, in the wild, it generally eats live aquatic insect larvae. In the aquarium, as well as consuming small flake food the Glowlight Tetra will enjoy brine shrimp, freeze-dried bloodworms, daphnia and tubifex worms. In addition, the Glowlight Tetra will benefit from pellet food, as most of these commercial foods include nutrients designed to enhance the vibrant colours of the fish.

The Glowlight Tetra is, by nature, a shoaling fish and it is generally recommended to purchase six or more fish, as their nature is to swim together as a shoal and they will tend to thrive much better as a shoal.

Glowlight Tetras are probably the second most popular freshwater tropical fish (next to the Neon Tetra. They are ideal to be kept in a mixed aquarium (or in a single-species aquarium) as a shoal and are both graceful and beautiful to observe. The smaller Tetras (including the Glowlight Tetra) are quite timid fish so should not be kept with large, aggressive species which may bully or even eat them.

Glowlight Tetras mix well with most other Tetras, Barbs, Danios, Guppies and other livebearers, dwarf cichlids, smaller Gouramis, catfish and loaches.

It is generally advised that the minimum tank size for Glowlight Tetras should be one of 24 inches in length, which will enable a small shoal to move around freely. The tank should be well-planted, preferably including dense foliage, in order to enable them to find cover and open space to enable them freely to swim.

Glowlight Tetras prefer slightly acidic water in nature because, in the wild, this is their natural habitat but I am bound to say that I have successfully kept Glowlight Tetras in water of only slightly acidic nature with a pretty neutral pH (percentage of Hydrogen) value and, of course, the Glowlight Tetras that you will buy are almost certainly commercially bred and, over many hundreds of generations of commercial breeding may well have adapted to the captive environment.

You can see from the image that the Glowlight Tetra is quite a distinctive fish. It is almost transparent, save for the line running from nose to tail and along the leading edge of the dorsal fin. The colour of these lines can range from orange to red. The Glowlight Tetra tends to occupy the area from the middle to the top of its environment and the line is not visible from underneath. Being almost transparent, the Glowlight Tetra is a difficult target and, like the Neon Tetra, the iridescent stripe will mirror back off the surface of the water to present a false target to prospective predators.

It is somewhat difficult to determine with certainty the sex of most Tetras. The female may have a rounder belly, particularly when she is gravid with eggs but, otherwise, it can be difficult to differentiate between the sexes.

The general rule for Tetras is that by keeping six or more of the same species in an aquarium they will be fully aware of which is male and which is female and they will act accordingly.

Most (but not all) Tetras have an additional fin which identifies them as being Tetras and the Glowlight Tetra is no exception. If you look between the dorsal fin and the caudal (tail) fin of the Glowlight Tetra you will observe a tiny, additional fin, known as the adipose fin. The purpose of this fin is not fully understood but, if it is present on a fish then you can be pretty certain that the fish is a Tetra.

Tetra comes from the Greek word “Tetragonopterus” which means square-finned and appears to relate to the four fins on vertical plane of the fish (dorsal, adipose, caudal and anal fins) which span the central line of the fish (when viewed from above or below, front or rear) and are not present as a pair (e.g. the pectoral fins).

The iridescence of your Glowlight Tetras may fade when the tank is dark and this is quite natural but if a Glowlight Tetra shows poor colouring compared with others then this is a sign that it may be ill so is best removed from the aquarium.

Glowlight Tetra – Video

How do Glowlight Tetras breed?

Tetras in general will scatter eggs by laying them over fine plants such as Fontanalis or Java Moss.

The male and female will roll over and the female will lay her eggs whilst upside down whereupon the male will fertilize them. Once laid, the parents will simply ignore them thereafter or eat them. In a community aquarium the eggs are likely to be eaten by other fish or, indeed, the parents so if you wish to preserve the eggs then you should move them into a breeding tank or, if you are keeping the parents in a breeding tank, remove them back to the community tank once the eggs are laid.

The most obvious ways to differentiate between the male and female Glowlight Tetra is that the female will have a slightly rounder belly, especially when gravid (carrying eggs).

Adult Glowlight Tetras will spawn every fortnight or so. 

Breeding tank for Glowlight Tetras

You should prepare an unlit tank of around 10 to 20 gallons in size with mature water. Ensure that there is plenty of fine vegetation (e.g. Fontanalis or Java Moss) in the tank. Gradually increase the amount of light in the tank until the Tetras breed if they do not begin their spawning behaviour readily.

You may wish to introduce mosquito larvae as an inducement to reproduction.

Another suggestion is to start with a half-filled tank and then to add water which may “fool” the fish into thinking that they are in their natural habitat and that it is raining. This can be made even more realistic by using some form of spray head, such as that found on a watering can or a showerhead – but ensure that the spray head and every other component is sterile and that the water is at the same temperature and condition as that in the tank, as your Tetras are sensitive to sudden changes in water temperature.

The male will swim quickly around, locking his fins when close to the female. Whilst spawning, both fish will roll over and, when upside down, the female will eject eggs and the male will fertilize them. Typically, the female will lay up to 150 eggs, which will land on the plants or fall to the bottom of the tank.

Once the female has scattered her eggs and the male has fertilized them then both should be removed carefully from the breeding tank because neither will have anything more to do with the eggs but they may simply eat them.

Turn the lights down or off because the eggs are particularly sensitive to the light.

The eggs will hatch typically in around 20 to 25 hours. 

The newly hatched fry can be fed infusoria (particularly rotifers) and will also thrive on egg yolk during the first two to four weeks. After around four days or so add baby brine shrimp. Once the fry are sufficient in size not to be treated as a snack then they can be introduced into the community tank where they will join the existing shoal.

Should your Glowlight Tetras have a special diet for breeding?

Adult Glowlight Tetras spawn every two weeks or so and don’t need any particular inducement to breed. That said, it has been suggested that adding mosquito larva may encourage them, presumably because the addition of a new food may “fool” the fish into thinking that it is breeding time. 

Mike Wheeler

I started keeping freshwater tropical fish in 1972 and it has been something of a passion ever since. In this website, my aim is to build up an everyman's guide to help the everyday aquarist get the best from this inspiring and entertaining hobby.

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