A female paratype of Spectrolebias gracilis from the Canabrava floodplains measuring 17.8 mm SL. It's likely that the females of S. gracilis and S. costae would be indistinguishable to most hobbyists, which is why knowing where your fish came from and avoiding population mixing can be critical to keeping captive species lines clean. Image credit: Costa & Amorim, CC BY 4.0

Spectrolebias gracilis sp. n., UFRJ 6441, paratype, female, 17.8 mm SL; Canabrava floodplains.