Hemigrammus erythrozonus was created in 1909.

Hemigrammus pulcher was created in 1938.

These little fish (Hemigrammus erythrozonus) have no easilly visible sexual differences util they are adult and ready to breed. At this time the females develop heavier,chubbier outlines than the males. This is due to the female filling with ova. (eggs). They are not easy to breed and are even harder to rear once they have been spawned.

well a gold tetra is called Hemigrammus rodwayi

The Ulreys Tetra (Hemigrammus ulreyi) comes from the tropics of Brazil and Paraguay. It is possible that some aquarium specimens have been released into the water ways in Oklahoma but I very much doubt if they could survive the winter temperatures in the wild if they had been released.