If you are looking for information about a 4-inch “true piraiba catfish” (Brachyplatystoma filamentosum), here’s what you should know: Meet the True Piraiba Catfish / Brachyplatystoma … True Piraiba Catfish (Brachyplatystoma filamentosum) – Aqua … True Piraiba Catfish / Brachyplatystoma Filamentosum for … True Piraiba Catfish / Brachyplatystoma Filamentosum for … Size: True piraiba catfish are among the largest freshwater fish in South America, reaching enormous sizes in the wild, up to 12 feet (3.6 meters) long and weighing over 400 pounds (180 kilograms). While you might find information on buying smaller sizes, a 4-inch specimen is a very young fish, and it will grow rapidly. Availability: Some exotic fish stores do sell juvenile piraiba catfish, including those in the 4-inch range. Diet: Even at a young age, piraiba catfish are predatory and will eat other fish small enough to fit in their mouths. As they grow, their diet primarily consists of other fish. Care: Keeping a true piraiba catfish in captivity is extremely challenging due to their eventual size and specialized needs. They require enormous tank space (thousands of gallons), strong water flow, and specialized care. This species is typically only suitable for very large public aquariums or experienced aquarists with exceptional resources. Important Considerations: Rapid Growth: Remember that a 4-inch piraiba will not stay that size for long. Be prepared for its rapid growth and the need for a massive aquarium or pond as it matures. Predatory Nature: Piraiba are fierce predators. They will eat smaller tankmates, so careful consideration is needed when choosing tank mates (if any). Environmental Needs: Mimicking their natural habitat is critical. This includes providing strong water flow, proper water parameters (temperature, pH, hardness), and ample space for movement. In summary, while it’s possible to find and purchase a 4-inch true piraiba catfish, it’s crucial to understand the significant commitment and resources required to provide appropriate care for this incredibly large and demanding species.