Gastrodermus hastatus

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The Gastrodermus hastatus, also known as the Tail Spot Pygmy Cory, is a tiny South American catfish recognized by its dark spot at the base of the tail and its tendency to spend more time in midwater than many other corydoras. Peaceful and highly social, it feels most secure in a group and brings activity to the middle levels of a planted aquarium. This wild-collected species has moderate availability in the aquarium trade and requires stable water, a non-abrasive substrate, and appropriately sized food. Its small adult size makes it a good choice for a carefully planned community aquarium.

General species description

The Gastrodermus hastatus belongs to the family Callichthyidae, a group of armored catfish characterized by two rows of bony plates. It differs from more strictly bottom-dwelling corydoras through its regular midwater swimming, especially when kept in a school. Keeping several individuals encourages natural behavior and reduces shyness. Despite its delicate appearance, it remains active when the water is well oxygenated and the aquarium provides plants, shelter, and quiet areas. This is a peaceful, schooling species that should be housed with small, non-aggressive tank mates. Since it is collected from the wild, careful acclimation and quarantine are especially advisable when new fish arrive.

Geographic origin and biotope

In Brazil, the Gastrodermus hastatus is associated with the Paraná and Paraguay river basins, where it inhabits small streams, side channels, and shallow marginal areas. Its natural habitat generally contains soft, slightly acidic water that may be stained by plant material, with light filtered by riparian vegetation. Flow is usually weak to moderate in the areas used by schools. In the aquarium, clean, well-oxygenated water free of accumulated waste is essential. A layout using roots, leaves, and fine-leaved plants can recreate the atmosphere of these quiet, shaded margins. Commercial availability is moderate, and wild fish may be sensitive to sudden changes in temperature or water parameters.

Precise location and local name

The range of the Gastrodermus hastatus includes tributaries and quiet areas of the Rio Paraná and Rio Paraguay basins in Brazil. It is not restricted to a single collection point, so the exact origin may vary between commercial shipments. In Brazilian stores and among aquarists, the scientific name Corydoras hastatus remains widely used, even though the species is now placed in the genus Gastrodermus. The English name Tail Spot Pygmy Cory directly describes its small size and the dark marking on the caudal peduncle. In French-speaking trade, Corydoras hastatus and dwarf tail-spot cory are commonly encountered. Trade names may be used for fish originating from different localities.

Appearance and physical characteristics

The Gastrodermus hastatus has a very short, laterally compressed body covered with the bony plates typical of corydoras. Its base color ranges from silvery gray to pale beige, with a dark lateral line and a clearly visible black spot on the caudal peduncle. The fins are usually translucent and may appear slightly yellowish depending on lighting and the fish’s condition. Its small, downward-facing mouth has sensitive barbels that help it locate food on the substrate. It may also use intestinal respiration, as do several members of its family, but this does not replace good oxygenation. Adult females are often broader and more robust than males, particularly when viewed from above.

General diet

The Gastrodermus hastatus is a small omnivore that searches for particles, microorganisms, and tiny invertebrates among the substrate and vegetation. In an aquarium, it accepts quality sinking tablets, micropellets, and finely chopped frozen foods. Baby brine shrimp, daphnia, and small bloodworms can supplement the diet without becoming the only food offered. Very small portions should be distributed so that all individuals can feed before faster tank mates consume everything. A varied diet supports body condition and breeding. Foods should be fine enough for its small mouth, and uneaten material should be removed promptly to protect water quality.

Essential data

• Origin river: Paraná and Paraguay river basins in Brazil
• Local name used: Corydoras hastatus; dwarf tail-spot cory
• Origin of the scientific name: The specific name hastatus refers to a spear-like or pointed shape
• Full-name etymology: Gastrodermus comes from the Greek gaster, belly, and derma, skin; hastatus comes from Latin and means spear-bearing or spear-shaped
• Common or vernacular names: Tail Spot Pygmy Cory, Corydoras hastatus, dwarf tail-spot cory
• Family: Callichthyidae
• Subfamily: Corydoradinae
• Name pronunciation: gas-troh-DER-mus has-TAY-tus
• Discovery: Carl H. Eigenmann and Rosa Smith Eigenmann, 1888
• Maximum adult size: About 2.5 cm
• Water temperature and pH: 22 to 27 °C; pH 6.0 to 7.5
• Stream appearance and surrounding vegetation: Small quiet streams, soft water, riparian vegetation, and subdued light
• Typical tank mates: Peaceful small characins, small loricariids, and other similarly sized corydoras
• Temperament and behavior: Very peaceful, schooling, active in groups, and often found in midwater
• Water depth: Shallow marginal areas
• Sexual dimorphism: Females are larger and rounder; males are smaller and more slender
• Bottom structure and flow: Fine sand or soft sediment, plant debris, and low to moderate current

In your aquarium

To succeed with the Gastrodermus hastatus, choose a mature, well-filtered aquarium with a soft substrate that protects the barbels. Keep it in a group, provide plants and shaded areas, and offer small varied meals. Stable temperature, pH, and water quality are more important than pursuing extreme values. Since the available fish are wild-collected and the species has moderate availability, slow acclimation and quarantine help reduce risks. Avoid territorial fish or tank mates large enough to intimidate it or treat it as prey.