Mollies generally come from Central and South America, and can be found from Mexico to Colombia. Black mollies belong to the live-bearing toothcarp family.
 
If kept correctly, mollies can grow to around 6 – 10 cm in length and live to be 5 years old. The males have larger dorsal fins than the females, making it easy to tell them apart. Like all livebearers, the males also have a modified anal fin, the gonopodium.