Red-tailed Hemiodus

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Hemiodus gracilis

Also known as: Slender Hemiodus, Redtail Hemiodus

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Description

Hemiodus gracilis, commonly known as the Red-tailed Hemiodus, is a characin species native to South America. It is characterized by its elongated, slender body and a distinctive red coloration on its caudal fin. These fish are known for their active swimming behavior and schooling tendencies, making them a striking addition to larger aquariums. In their natural habitat, they inhabit clear to blackwater rivers and tributaries, often found in areas with moderate to strong currents.

Physical Characteristics

Body shape: elongated
Coloration: Silvery body with a prominent, often intense, red caudal fin. A distinct black spot or blotch is typically present at the base of the caudal fin, extending onto the lower lobe. Some individuals may exhibit a faint lateral line.
Scale type: cycloid
Mouth position: superior
Distinctive features: Elongated, torpedo-shaped body, Bright red caudal fin, Black spot at the caudal fin base, Small, upturned mouth
Dorsal fin: Single, relatively small dorsal fin located mid-body.
Tail fin: Deeply forked caudal fin, with the lower lobe often more elongated and intensely red than the upper lobe. The black spot is a key feature here.
Pectoral fin: Small and transparent, positioned low on the body.
Distinctive fins: Adipose fin present, typical of characins.

Identification Tips

Caudal Fin Coloration

The most striking and reliable identification feature is the bright red caudal fin, often with a black spot at its base.

Body Shape

Its slender, elongated, and somewhat compressed body distinguishes it from more robust characins.

Mouth Position

The small, upturned mouth is indicative of its surface-feeding habits.

Habitat

Water type: freshwater
Depth: Typically found in mid-water to upper water columns.
Environment: Clear to blackwater rivers, streams, and tributaries. Prefers areas with moderate to strong currents, often associated with submerged vegetation, roots, and fallen branches. They are pelagic fish.
Geographic range: South America, primarily in the Amazon River basin, including tributaries in Brazil, Peru, Colombia, and Venezuela. Also found in the Guianas.

Aquarium Information

Care level: intermediate
Temperament: peaceful
Diet: omnivore
Minimum tank size: 75 gallons (280 liters)
Temperature: 72-82°F (22-28°C)
pH level: 5.5-7.5
Hardness: 2-15 dGH
Compatibility: Generally peaceful and can be kept with other similarly sized, non-aggressive characins, cichlids (e.g., Angelfish, Discus), catfishes, and loaches. Avoid very small or fin-nipping species.
Special requirements: Requires a well-filtered aquarium with ample swimming space. A tight-fitting lid is essential as they are known jumpers. Provide areas with dense planting along the perimeter and open swimming areas in the center. Substrate should be fine sand or smooth gravel. They thrive in schools of 6 or more individuals.

Wild Information

Conservation status: least concern
Seasonality: No specific seasonal patterns for availability in the aquarium trade, generally available year-round. In the wild, breeding may be seasonal, often coinciding with rainy seasons.
Market price: Moderate for aquarium trade
Commercial importance: medium
Taste: Not typically consumed due to size and bony nature.
Texture: Not typically consumed.
Nutritional value: Not typically consumed.

Key Facts

Surface Feederbehavior

Hemiodus gracilis primarily feeds on the surface, consuming small insects and plant matter that fall into the water.

Schooling Behaviorbehavior

These fish are obligate schooling fish, requiring a group of at least six individuals to thrive and exhibit natural behaviors.

Leaping Abilitybehavior

Red-tailed Hemiodus are known for their ability to leap out of the water, especially when startled or during feeding, necessitating a secure tank lid in aquariums.

Taxonomic Stabilityevolution

The taxonomy of Hemiodus gracilis has been relatively stable, with no major recent taxonomic changes or widely accepted synonyms beyond its original description.

Safety Information

Safe

Safety level: safe
Venomous: No
Edibility: not recommended
Handling notes: No specific handling precautions are required beyond standard fish handling practices to minimize stress. They are delicate and can be easily stressed during capture and transfer.

Similar Species

Hemiodus unimaculatus

While also having a black spot, H. unimaculatus typically lacks the intense red coloration on the caudal fin, which is usually more translucent or yellowish. Its body can also be slightly deeper.

Hemiodus argenteus

H. argenteus is generally larger and has a more uniformly silvery body without the prominent red caudal fin. It also possesses a distinct black lateral stripe that H. gracilis lacks.

Scientific Classification

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Characiformes
Family: Hemiodontidae
Genus: Hemiodus
Species: gracilis

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