South American freshwater stingray

The ocellate river stingray, Potamotrygon motoro, is a freshwater ray native to the Amazon, Orinoco, and Parana-Paraguay river systems of tropical South America. It is the most widespread member of the South American river stingray family and is easy to recognise by the orange-ringed eyespots, or ocelli, scattered across its sandy-brown disc. In aquariums it commonly reaches about 50 centimetres across the disc, and large specimens grow larger still. A venomous barb on the tail can deliver a painful, medically serious sting, so this animal demands respect and careful handling.

Motoros are bottom-dwelling predators that cruise the substrate hunting invertebrates, crustaceans, and small fish, and they bury themselves in sand to ambush prey and to rest. They are largely nocturnal and need a soft, smooth sand bed with no sharp decor that could tear the disc. This is an advanced fish: it produces a heavy bioload, demands pristine water, and is intolerant of nitrate and waste, so strong filtration and large, frequent water changes are essential. Suitable tankmates are calm, mid-water species that will not compete for food on the bottom.

Because of its adult size, a single motoro needs a very large, low tank of around 1000 litres or more with a wide footprint rather than height, kept warm at 24 to 28 degrees Celsius in soft, acidic water. Unlike most aquarium fish, stingrays are livebearers: after internal fertilisation the female carries the developing pups and gives birth to a small litter of fully formed miniatures, with around a dozen or more recorded in captivity. Breeding is realistic only for keepers with the space and filtration to house adults, so this is a long commitment rather than a casual purchase.