The checkered pupfish, Cualac tessellatus, is a cyprinodontid endemic to a handful of springs in the Río Verde valley, San Luis Potosí, Mexico. Listed as Endangered by the IUCN, it lives in the shallow margins of crystal-clear, very hard spring-fed pools, including the Media Luna lagoon system. It is rarely available in the hobby, and captive breeding depends on very hard water, with the best results where chunks of gypsum rock are left to dissolve.

Moderate