Black-belt Tetra - Hemigrammus kuroobi Fish Profile & Care Guide
Introduction
The Black-belt Tetra (Hemigrammus kuroobi) is a small characin in the genus Hemigrammus, described relatively recently in 2019 by Reia and Benine. It is a slender, laterally compressed tetra reaching around 4 to 5 cm in adult length, comparable in size to many familiar small tetras. The species is distinctive within its genus for its colour pattern, which combines a single, well-defined humeral blotch with a separate, dark mid-lateral stripe running along the body towards the tail. This striking stripe pattern is the basis for the name "kuroobi", taken from Japanese words for "black belt". Although it is recognised in the scientific literature, Hemigrammus kuroobi remains rare in the aquarium hobby, so most husbandry guidance is sensibly extrapolated from closely related Hemigrammus species rather than long experience with the species itself.
Like other members of Hemigrammus, the Black-belt Tetra can be expected to behave as a shoaling mid-water Tetra. The genus as a whole comprises peaceful, schooling fishes that naturally form loose groups, using lateral body markings and humoral spots as visual cues to maintain contact with conspecifics. In captivity, it is therefore prudent to treat H. kuroobi as a social species and keep it in a sizeable group rather than in isolated pairs or trios. Keeping at least eight to ten specimens together is likely to reduce nervous behaviour, encourage natural interaction, and help the fish display their full colour and pattern, mirroring the approach used successfully for other small Hemigrammus Tetras.
Black-belt Tetras are widely regarded as peaceful community fish. Suitable companions would therefore be other small, calm characins, pencilfish, rasboras, and peaceful Dwarf Cichlids, along with non-aggressive bottom dwellers such as Corydoras catfish and smaller Loricariidae. Robust but gentle Livebearers can also work, provided there are no significant differences in water chemistry requirements. Large predatory fish, boisterous species that might outcompete them at feeding time, and known fin-nippers should be avoided, as H. kuroobi is unlikely to cope well with sustained harassment or intense competition in a confined space.
Black-belt Tetras come from a classic blackwater environment with very soft, ion-poor, acidic water and high levels of dissolved humic substances. For aquarium care, it is sensible to recreate the broad features of these conditions rather than trying to match extremes precisely. Soft water with low general and carbonate hardness, a slightly acidic pH, and relatively low conductivity is appropriate, matching the general preferences documented for Hemigrammus species in aquaria. A long, well-covered tank, starting at around 60 litres for a group, with gentle filtration, subdued lighting, a dark substrate, and abundant plant cover or leaf litter will help the fish feel secure and encourage natural shoaling. As with other blackwater-associated Tetras, stable, very clean water and careful acclimation are more important than chasing exact numbers, and any adjustments to pH or hardness should be made gradually to avoid stressing this relatively delicate, wild-type species.
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Sexual Dimorphism
Sexual dimorphism in Black-belt Tetras is subtle to the casual observer but clearly defined in the species' formal description. Mature males develop a single small bony hook on each segment of the posterior branch of the first to fourth branched anal-fin rays, a feature that is absent in females and can be confirmed under magnification. As with many congeners, it is also reasonable to expect the usual characin pattern where males are a little slimmer and more streamlined, while females become deeper-bodied and noticeably rounder in the abdomen when full of eggs, with any differences in colour intensity likely to be modest rather than dramatic.
Quick Facts
| Scientific Name | Hemigrammus kuroobi |
|---|---|
| Year Described | 2019 |
| Kingdom | Animalia |
| Classification | Actinopterygii |
| Order | Characiformes |
| Family | Characidae |
| Genus | Hemigrammus |
| Origins | Brazil |
| Approx Max Size | 5 cm |
| Temperament | Peaceful |
| Aquarium Level | Middle |
| Difficulty | Beginner - Intermediate |
| Shoaling | Yes |
| Best kept as | Groups 8+ |
| Diet & Feeding | Omnivore |
| Reproduction | Egg-Scatterer |
| Average Lifespan | Up to 5 Years |
Water Parameters
| Water Type | Freshwater |
|---|---|
| pH | 4.5 - 7.0 |
| GH | 0 - 3 |
| KH | 0 - 2 |
| TDS | 30 - 120 |
| ℉ | 75 - 82 |
|---|---|
| ℃ | 24 - 28 |
Natural Habitat
The Black-belt Tetra is currently known only from its type locality in the upper Rio Negro drainage in Amazonas State, Brazil, where it was described from a small tributary of the Rio Miuá near São Gabriel da Cachoeira. This part of the Rio Negro basin is characterised by classic blackwater conditions, with tea-coloured, humic-rich water, very low mineral content, and a network of narrow forest streams and minor channels. These fish prefer quieter, marginal habitats with gentle flow, submerged roots, and leaf litter typical of upland Negro Basin streams. At present, there are no confirmed records of H. kuroobi outside this restricted upper Rio Negro area, so it should be regarded as a localised Brazilian endemic associated with blackwater tributaries of the Rio Miuá until broader survey data show otherwise.
Breeding
Breeding behaviour in Black-belt Tetras has not yet been described in detail in the scientific or hobby literature, but available reports of successful spawnings in aquaria, together with well-documented information from closely related Hemigrammus species, strongly indicate that it is a typical open-water egg-scattering characin with no parental care.
As with other small tetras in the genus, a sensible approach is to use a separate, dimly lit breeding tank with very soft, slightly acidic water, gentle filtration, and fine-leaved plants or spawning mops for the adults to scatter their adhesive eggs over. Offer a separate male and female, or a small group of adults, plenty of rich live and frozen foods for several days, then move them into the breeding tank late in the day, as many Hemigrammus tend to release their eggs at dawn and will quickly consume them if left in with the spawn.
Once eggs are seen, the adults should be removed, and the tank should be kept very dimly lit, as tetra eggs are often light-sensitive. In closely related Hemigrammus Tetras, the eggs usually hatch after about a day or two in suitably warm water, and the young first become free-swimming a few days later, when they must be started on very fine foods like infusoria or liquid fry preparations before moving on to newly hatched brine shrimp as they increase in size.
Diet & Feeding
Direct observations of the Black-belt Tetra feeding in the wild are not yet documented in detail, but its morphology and close relationship to other Hemigrammus species strongly suggest a diet of small aquatic invertebrates, insect larvae, micro-crustaceans and other zooplankton, with some opportunistic grazing on biofilm and fine organic particles. In the aquarium, H. kuroobi should therefore be treated as a small omnivorous micro-predator that thrives on a varied diet: good-quality, fine-grade flake or micro-granules as a staple, regularly supplemented with live and frozen foods such as daphnia, cyclops, baby brine shrimp, and finely chopped bloodworm. Providing this variety will support good condition, natural foraging behaviour and reliable spawning, while also helping to bring out the full intensity of the species' lateral stripe and body colouration, as is well established with other small Hemigrammus Tetras.
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Published: 11 Dec 2025
Last Updated: 11 Dec 2025