Bigtooth River Stingray

Potamotrygon castexi is broadly distributed across the Paraná and Amazon drainages of South America, one of the more commonly encountered freshwater rays in the ornamental trade after P. motoro. Its tan to brown disc bears irregular pale spotting and mottling that varies between populations, with some individuals showing quite attractive warm-toned patterns. It tolerates a somewhat broader range of water conditions than strictly Xingu or blackwater species, making it marginally more accessible for keepers who cannot achieve very soft, very acidic water. It has a well-established captive husbandry record and breeds readily when properly conditioned. A solid choice for keepers seeking their second or third ray species.

Water: 22–28°C, pH 6.0–7.5, soft to moderate (2–12 dGH); zero ammonia/nitrite, nitrate below 20 ppm. Tank: Minimum 500L, fine sand, open swimming floor, reliable high-capacity filtration. Feeding: Carnivore; earthworms, prawn, mussel, whitebait; transitions to frozen foods reliably. Breeding: Viviparous; litters 4–12 pups; one of the more reliably bred potamotrygonids in captivity. Compatibility: Large non-aggressive fish suitable; cohabitation with other rays possible in sufficiently large setups.