Tyttocharax is a genus of tiny characins from the western Amazon basin, recorded in the atlas from Peru, Brazil, and Colombia. Atlas species measure just 0.5–1.5 in, among the smallest fish in the entire characin family - true miniatures even by tetra standards. As in several other small Amazonian tetra genera, males carry specialized fin structures used in courtship display rather than the plain fins typical of most characins, a trait shared with their glandulocaudine relatives among the region's tetras.
Cochu's tetra (T. cochui) is the species aquarists are most likely to encounter, sold into the nano-aquarium hobby where its minute size suits small planted tanks and it shoals well in numbers; the Blackedge tetra (T. madeirae) turns up occasionally through the same specialist channels, while T. metae and T. tambopatensis are little known outside ichthyological collections. As with many soft-water Amazonian tetras, these fish do best in acidic, tannin-stained water that mimics their native blackwater and clearwater streams. Three of the four atlas species are assessed Least Concern; the fourth is Vulnerable, a reminder that even a wide genus can hold one narrower-range, more exposed species.