Nannostomus harrisoni

Adults grow up to 4 cm in length. Their body is elongated, with a pointed head, and their eyes are disproportionately large. Males are slimmer than females and have red pigmentation at the base of the caudal and anal fins. The fish's coloration is silvery, with a wide black stripe running along the body.

Its natural habitat is in South America. Nannostomus harrisoni is presumably endemic to the Demerara River, located in eastern Guyana. These fish inhabit small, slow-flowing rivers and streams, as well as swampy areas and floodplain lakes. Typical biotopes are characterized by abundant aquatic vegetation, numerous snags, and a bottom covered with plant debris and fallen leaves.

This is a peaceful and somewhat timid schooling fish that should not be kept with large or overly active species. It is recommended to maintain a group of at least 10 individuals, as Nannostomus behave more naturally in such numbers. Apistogramma, other small American cichlids, as well as Corydoras catfish and similar fish, make good tank mates.

For a group of 10 fish, the optimal aquarium volume is 50–60 L. It is desirable to keep Nannostomus harrisoni in conditions that are as close as possible to their natural habitat. The fish will look most expressive among snags and thickets of aquatic vegetation, including floating species, where they often gather. Lighting should be subdued, so shade-loving plants are chosen for decoration. An important, though not mandatory, decorative element is the leaves of some trees, which are placed on the bottom. As they decompose, conditions similar to natural bodies of water are created: the water is enriched with tannins and acquires a characteristic brownish tint. In addition, leaves serve as an ideal basis for the formation of colonies of beneficial microorganisms, such as paramecia, which are a valuable additional food source for fry. Long-term and successful keeping of the fish is ensured by maintaining stable water parameters within acceptable hydrochemical limits. For this, the aquarium is equipped with all necessary equipment, part of the water is replaced with fresh water weekly, organic waste is regularly removed, and other mandatory procedures are performed.

In a home aquarium, these fish readily accept various types of food. Dry foods, such as flakes and granules, can form the basis of their diet, but it is important to regularly offer them live or frozen brine shrimp, daphnia, small bloodworms, and other similar supplements.

The breeding process is associated with a number of difficulties, which include both creating suitable conditions and the peculiarities of fish behavior during spawning. However, the greatest difficulty is preserving the fry. When the fish are in an optimal environment and receive high-quality, protein-enriched food, they quickly reach spawning condition. Males actively court females, competing for the right to fertilize the eggs, which the females scatter haphazardly. Parental instincts are not developed in these fish. Immediately after spawning, adults can eat both eggs and newly hatched fry. To protect them, experienced aquarists plant dense thickets of low-growing plants or mosses, such as Java moss, on the bottom, or use special artificial spawning substrates. Eggs that fall among the vegetation have a significantly higher chance of survival. The incubation period lasts 1–2 days. Fry should be transferred to a separate tank with identical water parameters, equipped with a simple air-driven sponge filter and a heater. They do not require an additional light source. In the first days of life, juveniles need microscopic food, such as infusoria or special powdered foods. As they grow, they transition to brine shrimp nauplii and other suitable foods.

Specific diseases that affect only this particular fish species have not been identified. When kept in suitable conditions, including high water quality, a balanced diet, and peaceful tank mates, health issues usually do not arise. The most common cause of illness is a deterioration of living conditions, which weakens the immune system and makes the fish susceptible to infections that are always present in their environment. Upon noticing initial signs of sickness (such as lethargy, emaciation, refusal to eat, or clamped fins), it is crucial to immediately check the basic water parameters. Often, restoring acceptable living conditions will lead to self-recovery, but if the fish is too weak or has suffered visible damage, medicinal treatment may be required. For more details on symptoms and treatment methods, consult the section “Diseases of Aquarium Fish.”

When purchasing, choose active fish that stay in a school and demonstrate a natural horizontal body orientation. Avoid individuals with signs of emaciation, damaged fins, or visible spots on the body. Since the species often comes to market as accidental bycatch with other Nannostomus, carefully examine the fish for species-specific characteristics: the presence of a characteristic black stripe and red accents on the fins. In the store, the fish may look pale due to stress, but they should show curiosity and react quickly to food.