Elassoma is a genus of pygmy sunfish endemic to the southeastern United States, traditionally associated with the true sunfishes (Centrarchidae) but now usually placed in its own small family, Elassomatidae. The atlas's 7 species are among the smallest freshwater fish in North America, measuring only about 1 in to 2 in as adults, and are found in still or slow-moving, often vegetated or blackwater habitats across the Coastal Plain — spring runs, swamps, ditches, and acidic pond margins. Their tiny size, rounded fins, and reduced lateral line set them apart from typical sunfish, and most species live quietly among dense aquatic vegetation rather than in open water.
Pygmy sunfish have a devoted following among native-fish and nano-tank hobbyists, who prize breeding males' intense color — reds, blues, and iridescent flecks depending on species — displayed in small, densely planted, peaceful setups that suit their diminutive size far better than a typical community tank. Elassoma evergladei (Everglades pygmy sunfish) and E. zonatum (banded pygmy sunfish) are the most widely available species; several others, including E. boehlkei (Carolina pygmy sunfish) and E. okatie (bluebarred pygmy sunfish), have far narrower natural ranges. Conservation status varies sharply across the genus: four species are Least Concern, but two are Vulnerable and one — E. alabamae, the spring pygmy sunfish, confined to a small number of spring systems in northern Alabama — is Critically Endangered, making habitat and groundwater protection at those few sites a real priority for the species' survival.