Max Size: 3cm

Eilyos Tetra (Hyphessobrycon eilyos)

Eilyos Tetras are peaceful and undemanding and will acclimate to various conditions, although very hard water may prevent the fish from reaching their full potential when it comes to colour.

Like many other Tetras, planted aquariums with darker substrates or subdued areas will provide the best home and result in more vibrant colours and improved health. However, even though they are peaceful, these Tetras may nip the fins of long-finned species such as guppies or Siamese Fighting Fish, especially if the Tetras are kept in smaller numbers.

It would be best if you maintained Eilyos Tetras in a group of 8 or more individuals. Not only will they fare much better when in the company of their own kind, but it will also result in a far more effective, natural-looking shoal and make your fish feel more secure. In addition, you may also see some fascinating displays of fin flaring by rival males if several are present.

Ideal tankmates for your Eilyos Tetras would be other small and peaceful species such as Corydoras Catfish, Hatchetfish, Loaches, Rasboras, small to medium-sized Barbs, Gouramis and West African Dwarf Cichlids. In addition, because of their shape, you can also keep these Tetras with larger Cichlids such as Discus and Angelfish. Unfortunately, Eilyos Tetras can be easily frightened, so make sure you do not house them with much larger boisterous species.

You can distinguish Eilyos Tetras from other Tetra species as they lack the humeral and caudal spots as well as the presence of numerous dark chromatophores on the lateral surface of the body. In addition, the pelvic, caudal, adipose and caudal fins are all red, and these fish possess 7 to 11 maxillary teeth.

Tank Mates

1 ideal tank mate ideas for the Eilyos Tetra include:

Frail Gourami(Ctenops nobilis)
Quick Facts
Scientific NameHyphessobrycon eilyos
Other NamesNone
Aquarium LevelMiddle - Top
DifficultyBeginner - Intermediate
Best kept asGroups 8+
Lifespan3 - 5 years
Water Parameters
Water TypeFreshwater
PH5.5 - 7.5
GH1 - 12
75 - 82℉
23.9 - 27.8℃


Eilyos Tetra

Natural Habitat

Eilyos Tetras are endemic to the upper Rio Araguaia basin in Brazil in South America. They inhabit small and shallow clear waters that have a slow-flowing current. These waters are often stained brown from the release of tannins and other chemicals. The substrate in these habitats is usually sandy, and these Tetras gather around in small patches of aquatic vegetation and submerged wood in the form of roots and fallen branches.

Araguaia River


Eilyos Tetras will readily accept all kinds of food; however, it would be best to offer them a varied diet. Their diet should consist of high quality dried foods such as micropellets, flakes and granules, as well as live and frozen fare such as vitamin-enriched brine shrimp, bloodworm, white mosquito larvae, daphnia and brine shrimp. In addition, it would be better to feed your Eilyos Tetras once or twice a day, only providing what they can consume within 3 minutes or less.

Sexual Dimorphism

It is relatively simple to differentiate between male and female Eilyos Tetras. Males will usually develop extended anal and dorsal fins as they grow and are generally larger, slimmer and more colourful than females.


Unfortunately, there is little to no information on Eilyos Tetras; however, they probably breed in a similar fashion to other Hyphessobrycon species.

To successfully breed Eilyos Tetras and increase the yield of fry, you will need to set up a separate breeding tank. The breeding tank needs to be dimly lit and contain bundles of fine-leaved plants such as java moss to give your fish somewhere to deposit their eggs. Spawning mops will work just as well. Alternatively, you can cover the bottom of the tank with some mesh with large enough holes for the eggs to drop through but small enough so the adults cannot reach them.

The water should be soft and acidic, with a pH level of between 5.5 and 6.5. The waters hardness should be between 1 and 5, and the temperature needs to be between 80 and 84 degrees Fahrenheit. In addition, filtering the water through peat is helpful, as is the use of RO water. Lastly, the tank will require a small air-powered sponge filter to provide a gentle current.

You can spawn Eilyos Tetras in a group, with half a dozen individuals of each sex being an ideal number. Make sure you condition your group with plenty of small live, frozen or freeze-dried foods, and spawning should not bestow too many problems. Alternatively, you can spawn your fish in pairs, conditioning female and male groups in separate tanks. Then, once the females are noticeably full of eggs and the males are displaying their best colours, select the plumpest female and best-coloured male and transfer them into the spawning tank that night. Your fish should then spawn the following morning. In either situation, the adults will eat the eggs if given a chance; therefore, you must separate the eggs as soon as you spot any.

The eggs will usually hatch between 24 and 36 hours later, and the fry will become free swimming around five days after that. It would be best to feed the fry on an infusoria type food for a few days until they are big enough to take brine shrimp nauplii, microworm and crushed flake food.

The eggs and fry are sensitive to light in the early stages of life, and you should keep the tank in darkness if at all possible.

Other Tetras of interest

African Moon Tetra(Bathyaethiops caudomaculatus)
African Red Eyed Tetra(Arnoldichthys spilopterus)
Black Darter Tetra(Poecilocharax weitzmani)
Black Line Tetra(Hyphessobrycon scholzei)
Black Neon Tetra(Hyphessobrycon herbertaxelrodi)
Black Phantom Tetra(Hyphessobrycon megalopterus)
View all Tetras
Date Added: 06/10/2021 16:17:21 - Updated: 22/11/2021 17:13:39