Polka-dot Freshwater Stingray

Potamotrygon rex was formally described in 2016 from the upper Tocantins River drainage in Goiás state, Brazil, where it inhabits rocky and sandy substrates in clear, warm water. Its common name alludes to the regal pattern: widely spaced, large, well-defined white to pale yellow spots on a dark brown to black disc, intermediate in spot density between the densely spotted P. henlei and the more sparsely spotted P. leopoldi. Adults reach 50cm disc width and are genuinely impressive specimens. In captivity it follows the standard care protocol for Xingu-Tocantins potamotrygonids: warm, very soft, mildly acidic, pristine water. It is now bred by European specialists and captive-bred individuals are increasingly available.

Water: 24–28°C, pH 5.5–6.8, very soft (1–6 dGH); zero ammonia/nitrite; large frequent water changes recommended. Tank: Minimum 600L, fine sand, open base, efficient high-capacity filtration; avoid calcareous substrates. Feeding: Carnivore; earthworms, prawn, mussel, cockle, frozen bloodworm; varied diet maintains vibrant colouration. Breeding: Viviparous; captive breeding being established by European specialists; litters 2–6 pups. Compatibility: Large, non-aggressive fish only; dedicated stingray display strongly recommended.