Hemigrammus erythrozonus

Glowlight Tetra

Classification

Characidae

Distribution

Known only from the Rio Essequibo, Guyana. Don’t expect to see any wild specimens for sale, though. All fish entering the trade are mass bred on commercial farms in various parts of the world. Most of the ones on sale in the UK originate from Eastern Europe.

Habitat

The Essequibo is the longest river in Guyana, and flows through a variety of biotopes. H. erythrozonus is found primarily in forested areas, in tributaries off the main river channel. The water here is typically stained a dark brown with tannins from decaying organic material and is often highly acidic as a result.

Maximum Standard Length

1.6″ (4cm).

Aquarium SizeTop ↑

A 24″ x 15″ x 12″ (60cm x 37.5cm x 30cm) – 70 litre tank could house a small group of these comfortably.

Maintenance

As it’s commercially bred in such huge numbers, it is adaptable and will do well in most tanks. It does look particularly effective in a heavily-planted arrangement, and can appear a little washed out in very spartan setups.

If you really want to see it at its best, you could set up a biotope tank. Use a substrate of river sand and add a few driftwood branches (if you can’t find driftwood of the desired shape, common beech is safe to use if thoroughly dried and stripped of bark) and twisted roots. A few handfuls of dried leaves (again beech can be used, or oak leaves are also suitable) would complete the natural feel. Allow the wood and leaves to stain the water the colour of weak tea, removing old leaves and replacing them every few weeks so they don’t rot and foul the water. A small net bag filled with aquarium-safe peat can be added to the filter to aid in the simulation of black water conditions. Use fairly dim lighting. Under these conditions the true beauty of the fish will be revealed.

Water Conditions

Temperature: 75-82°F (24-28°C)

pH: 5.5-7.5. Although it will survive in slightly alkaline water, it tends to be more colourful when kept in acidic conditions.

Hardness: 2-15°H

Diet

Easy to feed. It will readily accept just about anything offered. For the best condition and colours, offer regular meals of small live and frozen foods such as bloodworm, Daphnia and brine shrimp, along with dried flakes and granules.

Behaviour and CompatibilityTop ↑

One of the best tetras for the ‘general’ community setup. It is lively, quite colourful and peaceful. It’s a good tankmate for most livebearers, danios, rasboras, other tetras and peaceful bottom dwellers such as Corydoras or smaller Loricariids. It can also be kept with the majority of commonly available gouramis and dwarf cichlids. Obviously, it isn’t safe with larger species that may see it as food, such as angel fish. In a biotope tank as described above, it can be combined with other Hemigrammus or Hyphessobrycon species, pencil fish, Apistogramma dwarf cichlids and the aforementioned bottom dwellers.

Always buy a group of at least 6 of these, preferably 10 or more. It is a shoaling species by nature, and will fare much better when in the company of its own kind. It actually looks far more effective when maintained like this anyway.

Sexual Dimorphism

Mature females are more rounded in the belly than males, and tend to grow a little larger.

Reproduction

Quite easily bred, although you’ll need to set up a separate tank in which to do so if you want to raise any numbers of fry. Something around 18″ x 10″ x 10″ in size is fine. This should be very dimly lit and contain clumps of fine-leaved plants such as java moss or spawning mops, to give the fish somewhere to deposit their eggs. Alternatively you could cover the base of the tank with some kind of mesh. This should be of a large enough grade so that the eggs can fall through it, but small enough so that the adults cannot reach them. The water should be soft and acidic in the range pH 5.5-6.5, gH 1-5, with a temperature of around 80-84°F. Filtering the water through peat is useful, as is the use of RO water. A small air-powered sponge filter bubbling away very gently is all that is needed in terms of filtration.

It can be spawned in a group, with half a dozen specimens of each sex being a good number. Condition these with plenty of small live foods and spawning should not present too many problems.

Alternatively, it can be spawned in pairs. Under this technique the fish are conditioned in male and female groups in separate tanks. When the females are noticeably full of eggs and the males are displaying their best colours, select the fattest female and best-coloured male and transfer them to the spawning tank in the evening. They should spawn the following morning. Interestingly, during the act itself the pair often turn completely upside down.

In either situation, the adults will eat the eggs given the chance and should be removed as soon as eggs are noticed. These will hatch in 24-36 hours, with the fry becoming free swimming a 3-4 days later. They should be fed on an infusoria–type food for the first few days, until they are large enough to accept microworm or brine shrimp nauplii. The eggs and fry are light sensitive in the early stages of life and the tank should be kept in darkness if possible. Average brood size per female is 120-150.

NotesTop ↑

This species is ubiquitous in most dealers’ tanks and is one of the best choices for the newcomer to fishkeeping, being both hardy and inexpensive. There is a selectively-bred albino form that has been produced for the trade and has become popular in recent years. Care for this is identical to the standard form.

Like all Hemigrammus, the taxonomic status of this species is currently Incertae Sedis, meaning uncertain. The genus is currently used as something of a catch-all for over 70 species of small characin. Most experts agree that a full revision is required, with the likely outcome that many species will be placed into new or different genera.