Brittanichthys is a genus of diminutive characins from the Amazon basin and the Guiana Shield, with atlas records from Brazil and Guyana. Its two species, axelrodi and myersi, are tiny even by tetra standards, reaching only 1–1.5 in, and share the deep-red body color and compact, deep-bodied profile typical of the small blackwater characins that crowd this corner of South American ichthyofauna.
Brittanichthys axelrodi, marketed as the blood red tetra, is the species most likely to reach hobbyists - a striking, saturated-red nano fish kept by specialist blackwater aquarists in soft, tannin-stained water that mirrors its native habitat, usually shoaled in numbers to bring out its color. Brittanichthys myersi has essentially no trade footprint by comparison. Both species are currently assessed Least Concern, which fits a genus that, while tied to specific blackwater habitats, has not been flagged for population decline in the available assessments.