Rhoadsia

In their natural habitat, adult individuals can reach 17 cm in length, but in a home aquarium, their size rarely exceeds 10–12 cm. It is important to note that these dimensions are characteristic of males; females are usually significantly smaller. The coloration of these fish has a silvery hue, which, depending on the lighting, can shimmer with iridescent colors. A distinctive feature is a large black spot located on the caudal part of the body.

The high-finned Rhoadsia inhabits freshwater bodies in western Ecuador and Costa Rica. In natural conditions, the fish prefer biotopes with clean, oxygen-rich water. The temperature regime in their habitats corresponds to a tropical climate, usually ranging from 22–25°C.

This is an active and temperamental fish that is more comfortable in a group. It is recommended to acquire them in a shoal of 5–6 individuals. Although Rhoadsia do not exhibit pronounced territorial behavior, they can become aggressive towards slower or smaller aquarium inhabitants if there is insufficient space. They are also prone to damaging the fins of other fish. They get along well with active fish of a similar size that inhabit the upper water column, as well as with robust catfish, such as Armored Catfish or Plecostomus.

For a small shoal of these fish, an aquarium of at least 200 liters will be optimal. The decor should include shelters and sufficient open space for swimming. It is recommended to use dark substrate — sand or gravel. Lighting should be subdued, and floating plants can create additional shading; if the light is too bright, the fish's coloration may fade. In nature, Rhoadsia inhabit diverse conditions: from fast, shallow rivers to stagnant swamps subject to heavy rainfall, as well as river estuaries with brackish water. However, acclimatized individuals, or those born in captivity, usually thrive in soft, slightly acidic water. Before acquiring these fish, it is important to clarify their keeping conditions to provide them with the most similar environment possible.

Rhoadsia are considered an omnivorous species. They readily accept various types of food: dry, frozen, and live. When choosing a diet, preference should be given to protein-rich foods.

Breeding is possible in a large aquarium of at least 1000 liters. The process involves forming a pair or a harem, where the dominant male exhibits territorial behavior and guards the egg clutch. After the fry become free-swimming, they are fed infusoria, followed by a transition to Artemia nauplii.

No specific species-specific diseases have been described for Rhoadsia altipinna; however, the fish are susceptible to typical characin infections if keeping conditions are violated. The main risk factors are the accumulation of organic waste in the water and insufficient aeration, which can lead to the development of bacterial lesions of the fins and skin.

To prevent diseases, the following rules must be observed:

• maintain stable water parameters and perform regular water changes to prevent nitrate accumulation
• ensure powerful filtration and constant oxygen saturation of the water, as the species is sensitive to environmental quality
• avoid overpopulation of the aquarium, which provokes stress and intraspecific aggression, often leading to injuries and subsequent secondary infections

When selecting individuals, attention should be paid to the activity of the fish and the absence of visible damage to scales or fins. Given the territorial nature of the species, it is important to assess compatibility with other aquarium inhabitants before purchase. Healthy fish should show interest in food and have clear eyes without cloudiness.