Xenotoca is a genus of fish in the family Goodeidae from Mexico, where various species are found in a wide range of habitats, from rivers and creeks to pools and lakes, in the Lerma–Grande de Santiago, Panuco, Cuitzeo and other basins of the Mesa Central. While no goodeid is a very common aquarium fish, the redtail splitfin (X. eiseni), is one of the most common aquarium goodeids; its bright colors offset its reputation for being aggressive towards and occasionally even killing tankmates. Similarly to X. eiseni, two species described in 2016 have males with red-orange tails, but this feature is not shared by the remaining members of the genus. All Xenotoca species are relatively small, reaching up to 9 cm (4 in) in standard length.

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