Hypoplectrus gemma (blue hamlet) is a tropical fish native to the Western Central Atlantic, including southern Florida, the Florida Keys, the Bahamas and the Arrecife Alacranes of Mexico. It is not found outside of this region. The fish is an iridescent blue color with thin dark borders along its tail. It is typically a shy species, preferring to hide among rock work or hover near the substrate. In the wild, Hypoplectrus gemma can grow to 13 cm and has a minimum population doubling time of less than 15 months. This species was discovered by Good and Bean in 1882.