Ulrey's Tetra

Adults of this tetra typically reach a length of up to 5 cm. Their body is predominantly gray, with a silvery belly and transparent fins. A small yellow streak is noticeable on the dorsal fin. A distinctive feature is a thin horizontal stripe, consisting of black and yellow colors, which runs from the head to the tail. Sexual dimorphism is weakly expressed: females are generally slightly larger than males.

The natural habitat of this fish is the Paraguay River basin, a tributary of the larger Paraná River; the species is known only from the Brazilian part of that basin. It prefers small streams and channels with calm currents, where aquatic vegetation is abundant.

This peaceful and calm species cannot compete with faster and more active fish. Therefore, for tankmates for the Yellow Tetra, it is advisable to choose species of similar size and temperament – these can be other characins, cyprinids, livebearers, and some South American cichlids. Optimal keeping involves a school of at least 6–8 individuals.

For a small school of Ulrey's Tetras, an aquarium of at least 70 liters will suffice. For decoration, sandy substrate can be used, supplemented with shelters made of snags, roots, or tree branches. Plants are recommended to be placed in groups, and floating vegetation will help create additional shading. To recreate conditions close to their natural habitat, alder cones can be added to the filter, or a small bag of them can be placed in the aquarium. Peat should only be purchased from pet stores, ensuring it has been pre-treated. Over time, the water will acquire a slight brownish tint. A similar effect can be achieved by using tree leaves, pre-dried and soaked until they begin to sink. Leaves are placed at the bottom of the aquarium and replaced approximately every two weeks. Aquarium care includes weekly replacement of 15–20% of the water volume with fresh water, as well as regular cleaning of the substrate from organic pollutants such as excrement and uneaten food residues.

The diet of these fish can include all types of dry, frozen, and live foods of appropriate size. A varied diet, such as a combination of dry flakes, pellets with bloodworms or daphnia, not only maintains the vitality of the fish but also enhances the richness of their coloration.

Ulrey's Tetra is an egg-laying species, with poorly developed parental instincts. This means that eggs and hatched fry can be eaten by their own parents. Therefore, for successful breeding, it is recommended to use a separate spawning aquarium. Usually, a tank of about 20 liters is used for these purposes; its decoration does not play a significant role. To protect future offspring, the bottom can be covered with a fine-mesh net, a layer of balls 1–2 cm in diameter, or dense thickets of low-growing, small-leaved plants or mosses. The aquarium is filled with water from the main tank immediately before placing the fish there. Only a simple sponge air-lift filter and a heater will be needed. A special lighting system is not required, as Ulrey's Tetras prefer subdued light during spawning. A stimulus for spawning will be establishing pH values between 5.5–6.5 and dGH from 1 to 5, at a temperature of about 26–28°C. The diet of the breeders should predominantly consist of protein-rich food (e.g., bloodworms, daphnia, brine shrimp). After some time, it can be noticed that some females will become significantly rounded – this will indicate that they are full of eggs. After this, the females and the largest, brightly colored males are transferred to the spawning tank. After spawning, the adult fish are returned to the main aquarium. Fry appear after 24–36 hours and begin to swim independently on the 3rd–4th day, after which they require special food for aquarium fish fry.

The best guarantee of fish health from any disease is a balanced aquarium biosystem with optimal keeping conditions. Therefore, if you notice changes in behavior, fish coloration, the appearance of uncharacteristic spots, or other symptoms, you should first check the water parameters, and only after that proceed with treatment measures.

When choosing Ulrey's Tetras in a store, attention should be paid to the overall activity of the school and the cleanliness of their skin. Healthy individuals should be active, without visible damage, ulcers, white film, or signs of emaciation. Avoid purchasing fish that appear sluggish, stay isolated near the surface, or have an unnaturally bloated abdomen. Since this species is often confused with other characins, carefully examine the pattern: a characteristic feature is an interrupted black and yellow stripe along the body. Given the rarity of the species in sales, ensure that the conditions in the store's aquarium meet basic requirements, as stress from poor water parameters can provoke the development of hidden diseases after transfer.