Characidium fasciatum

Adults reach 6–7 cm. Their elongated body shape resembles some loaches, such as the Chinese algae eater, the stone loach, or the kuhli loach. The predominant colour is grey. Depending on the population's origin, the body may bear black spots running along a dark horizontal stripe, or streaks that begin at the back.

Characidium fasciatum comes from South America. It inhabits the São Francisco River basin and the upper Paraná River in eastern Brazil. It prefers river reaches with sandy-pebble substrate and moderate water flow.

These peaceful, calm fish prefer to stay in groups of at least 6. They get along well with other non-aggressive species that also tolerate relatively cool water, such as goldfish.

A group of 6–8 fish needs an aquarium of 80–100 L or more. Since these fish prefer the bottom level, pay special attention to the lower part of the tank. Use fine gravel or coarse sand as substrate. Place stones, boulders and driftwood to create plenty of shelter. Live aquatic plants are not necessary. Characidium fasciatum needs moderate water flow, which a good internal filter can provide. Remember that this species tolerates high water temperature poorly; the optimal range is 18–24°C, so a heater will likely not be needed. In nature they eat small aquatic invertebrates such as small crustaceans, worms and insect larvae. In the aquarium, their diet can consist of any sinking, protein-rich dry food: flakes and granules.

In nature these fish eat small aquatic invertebrates such as small crustaceans, worms and insect larvae. In the aquarium, their diet can be based successfully on sinking, protein-rich flakes and granules. This peaceful, calm fish does best in a group of at least 6 individuals. They get along well with other non-aggressive species that also prefer relatively cool water, such as goldfish.

At present, reliable information on breeding Characidium fasciatum in the aquarium is scarce. Because the species is rare in trade, successful breeding is mostly reported by experienced aquarists working with wild-caught fish. Specific conditions that mimic the natural habitat are recommended, but no standard protocol has been established.

The species shows relative disease resistance when water parameters are maintained. The main health risk comes from solitary keeping or unsuitable conditions, which cause severe stress and lower immunity. Characidium fasciatum is sensitive to high temperature and low oxygen. Prevention involves keeping the water clean, regular water changes, and providing enough shelter to reduce stress.

When buying, watch for activity: healthy fish should show interest in their surroundings, stay in the bottom layer, and show no signs of emaciation. Avoid specimens with damaged fins, a coating on the body, or abnormal behaviour (lethargy, staying at the surface). Since the species is rare, buy a group of 6 or more to ensure their social well-being.