Atya scabra

The Brush Shrimp is a unique and fascinating freshwater crustacean known for its filter-feeding habits and preference for tanks with strong water movement. This relatively large shrimp is a peaceful and sedentary species that spends most of its time perched on rocks or driftwood, extending its fan-like appendages to catch microscopic food particles from the water column. Due to its social nature, it should be kept in small groups to help it feel secure and exhibit its natural behaviors. They thrive in a well-established aquarium with stable and clean water.

As a detritivore, its diet consists mainly of fine-particle foods. In an aquarium, this can be supplemented with crushed flakes, powdered fry food, or specialized foods for filter-feeding shrimps, all of which should be introduced into the water current. They are also excellent at consuming biofilm that grows on tank surfaces. While they are not overly demanding, their need for high oxygen levels and strong water flow places them in the medium difficulty category, making them a better choice for aquarists with some experience. With proper care, these interesting creatures can live for many years, making them a long-term addition to a suitable community tank.

The Brush Shrimp, Atya scabra, is a captivating invertebrate native to fast-flowing freshwater rivers and streams across the Americas and Africa. Often sold under names like Rock Shrimp or Hairy-legged Shrimp, its unique lifestyle and requirements make it a rewarding but moderately challenging species for the dedicated hobbyist. It is a filter-feeder that has adapted perfectly to a life in high-current environments. In an aquarium setting, replicating this habitat is the most critical component of its care. A powerful filter outflow or one or more powerheads should be used to create significant and consistent water movement throughout the tank. This flow is not only for comfort but is essential for both feeding and respiration, as this species has a high demand for oxygen.

These shrimp are primarily sedentary, preferring to find a secure spot on a piece of driftwood, rock, or sturdy plant and face into the current. From this vantage point, they use specialized, fan-like front appendages to filter microorganisms, algae, and detritus from the water. An aquarist must ensure a steady supply of this microscopic food. In a new or overly clean tank, they can starve. A mature aquarium with an established biofilm is beneficial. Their diet should be supplemented daily by releasing finely ground pellets, wafers, or frozen foods into the current upstream from their position. This allows them to catch the particles as they drift by. If the shrimp are observed frequently picking at the substrate with their claws instead of filter-feeding, it is often a sign of insufficient food in the water column.

Socially, they are peaceful and non-aggressive. They are shoaling animals that require the company of their own kind to feel secure, so a minimum of three individuals is recommended. When housed together, they often congregate in the same high-flow area of the aquarium. They are slow-moving and defenseless, making them unsuitable for tanks with large, aggressive, or boisterous fish that might harass them or steal their food. They primarily occupy the bottom and middle swimming zones. Due to their moderate waste production and significant adult size, they contribute a noticeable bioload to the aquarium and require a tank of a generous size to accommodate their needs and maintain stable, clean water conditions within a moderate temperature range.

Atya scabra is a validated species of freshwater decapod crustacean belonging to the family Atyidae. Its geographic distribution is notably widespread, encompassing river systems in both the Americas and western Africa that have access to the sea, a key factor in its reproductive life cycle. Morphologically, A. scabra exhibits a depressiform body shape, which provides a low profile and hydrodynamic stability, allowing it to anchor itself effectively against strong currents on benthic substrates. This adaptation is crucial for its survival in the high-velocity lotic environments it inhabits.

The species' primary ecological role is that of a specialized suspension-feeding detritivore. It utilizes chelipeds that are modified into fan-like structures to filter fine organic particulate matter, biofilm, and microorganisms from the water column. This feeding mechanism makes it an important contributor to nutrient cycling within its ecosystem by converting suspended detritus into faunal biomass. Physiologically, A. scabra is characterized by a high oxygen consumption rate, a direct adaptation to the oxygen-saturated waters of its natural habitat. Conversely, it possesses a low metabolic rate, consistent with its largely sedentary behavior, which involves long periods of stationary filter-feeding. Its bioload factor is moderate, reflecting a medium level of waste production relative to its body mass.

This species belongs to a group of amphidromous shrimp, where adults reside and spawn in freshwater, but the planktonic larvae must drift downstream to brackish or marine environments to undergo development before migrating back upstream as post-larvae. This complex life history is the primary reason for its breeding difficulty in captivity. From a conservation standpoint, Atya scabra is listed as Least Concern (LC) on the IUCN Red List, indicating that it currently has a stable and widespread population with no immediate threats to its survival.

Successfully breeding the Brush Shrimp in a home aquarium is considered exceptionally difficult and is rarely achieved by hobbyists. The primary challenge lies in its complex reproductive strategy, which requires both freshwater and saltwater conditions to complete. Because of these specific and demanding requirements, this species is not recommended for those new to invertebrate breeding.

These shrimp are amphidromous, meaning the adults live and mate in freshwater, but the larvae cannot survive in it. Identifying males and females can be challenging, but as with many related shrimp, females may grow larger than males and possess a broader, more curved carapace and pleura (abdominal plates) to accommodate eggs. For a healthy group dynamic, a ratio of at least one male to two or more females is advisable.

In a mature aquarium, a healthy female may become 'berried,' carrying a clutch of very small eggs under her tail. She will fan and care for these eggs until they hatch. Upon hatching, countless minuscule, planktonic larvae are released. In a standard freshwater tank, these larvae will perish within a few days. For any chance of success, the larvae must be immediately siphoned out and transferred to a separate, dedicated larval rearing tank with brackish or full marine salinity. This transition is the first critical hurdle.

The subsequent challenge is raising the delicate larvae in the saltwater environment. This requires precise control over salinity, temperature, and water quality. The larvae are filter-feeders and must be provided with a constant supply of microscopic food, such as live phytoplankton or specialized liquid fry food. After several weeks of development through various larval stages, the survivors will metamorphose into post-larval shrimp, which resemble miniature versions of the adults. These post-larval shrimp must then be painstakingly and slowly acclimated back to full freshwater over a period of days or weeks before they can be moved to a standard aquarium. Due to this intricate process, breeding is typically an endeavor for public aquaria or highly specialized breeders.