Hoplisoma sterbai

This species is a fascinating benthic, or bottom-dwelling, fish native to the freshwater river systems of South America. In its natural environment, it inhabits slow-moving waters that are typically soft and slightly acidic. To create an ideal habitat in an aquarium, it is best to replicate these conditions with gentle water flow and stable, warm temperatures. A soft, sandy substrate is highly recommended to protect the fish's sensitive barbels, which it uses to search for food without risk of injury. Sharp or coarse gravel should be avoided. As a highly social animal, it exhibits strong schooling behavior and must be kept in a group of its own kind. A minimum school size is necessary for the fish to feel secure; a larger group will result in more confident and natural behavior, creating a captivating display as they move and forage together. Their moderate activity level consists of constantly exploring the tank bottom.

Physiologically, this fish possesses a remarkable adaptation for low-oxygen environments: the ability to breathe atmospheric air. It will occasionally dash to the surface for a gulp of air, which is absorbed through its intestines. This is normal behavior and not necessarily a sign of poor water quality, although it may become more frequent if oxygen levels are depleted. As an omnivore with a daily feeding frequency, it requires a diverse diet. While it will consume high-quality sinking pellets and wafers as staples, its health and vitality are significantly improved by regular offerings of frozen and live foods. Its peaceful temperament makes it an excellent resident for a community tank, provided its tank mates are also non-aggressive and do not compete for food at the bottom. Due to its relatively low waste production and metabolism, it contributes a moderate bioload to the aquarium ecosystem.

Belonging to the family Callichthyidae and the order Siluriformes, this species is a neotropical freshwater catfish. Previously classified within the large genus Corydoras, recent phylogenetic studies have led to its reclassification into the genus Hoplisoma. Its morphology is well-adapted for a benthic lifestyle. The body is fusiform, though ventrally flattened, allowing it to rest and move efficiently along the substrate. Like other members of its family, its body is protected by overlapping bony plates or scutes rather than scales. Notable features include its large eyes, adapted for foraging in the dimmer light conditions of riverbeds, and a round-bodied profile.

Physiologically, it is characterized by a low metabolic rate, low oxygen consumption, and consequently, a low rate of waste production, giving it a modest bioload factor. A key physiological trait is its capacity for facultative aerial respiration. In hypoxic conditions, it can supplement gill respiration by swallowing air at the surface, which is then absorbed by a highly vascularized posterior intestine. This adaptation is critical for survival in its native habitats, which can experience fluctuating dissolved oxygen levels. Ecologically, it functions as a benthic omnivore, playing a role in bioturbation. Its foraging behavior, which includes rooting through sediment and consuming biofilm, helps to aerate the upper layers of the substrate and process detritus. Its origin in specific South American river systems dictates its preference for soft, slightly acidic water with low dissolved solids. According to the IUCN Red List, its conservation status is categorized as Least Concern (LC), indicating that it is not currently at high risk of extinction in its natural range.

Breeding this species is considered moderately difficult and is an achievable goal for the dedicated hobbyist who can provide specific conditions. Success begins with establishing a healthy, well-conditioned group in a dedicated breeding aquarium. A recommended ratio is two or more males for every female to increase the chances of a successful spawn. Distinguishing between sexes can be subtle; females are typically larger, wider, and have a more rounded underbelly compared to the smaller, more slender males, a difference that becomes more apparent as females become gravid with eggs.

To condition the fish for spawning, provide a rich and varied diet high in protein, focusing on live and frozen foods for several weeks. The spawning itself is often triggered by simulating rainy season conditions. This is best achieved by performing a significant water change with water that is slightly cooler than the aquarium's current temperature. This temperature drop, combined with the pristine water, often stimulates courtship behavior. The spawning process is distinctive; the male and female will engage in a courtship ritual where the female gathers sperm before depositing her adhesive eggs. She will typically choose flat surfaces such as the aquarium glass, plant leaves, or spawning mops to lay a small clutch of eggs, a process that may be repeated over several hours.

Once spawning is complete, it is crucial to remove the adult fish from the breeding tank, as they will consume the eggs. The eggs should be kept in well-aerated water to ensure a high hatch rate; some breeders add an anti-fungal agent as a preventative measure. After a few days, the fry will hatch and initially survive by consuming their yolk sacs. Once the yolk sacs are depleted, they must be fed microscopic foods. As they grow, their diet can be transitioned to newly hatched live foods and finely crushed flake or fry powder. Maintaining excellent water quality through small, frequent water changes is critical for the survival and healthy development of the fry.