Natural Wild Life | Molly | The molly is a small-sized tropical fish that is found naturally in the warm and peaceful rivers of Central America. Today, mollies are extremely popular fish to be kept in the community of an artificial aquarium, all around the world. Mollies are known for their calm and peaceful nature, which along with their brightly coloured bodies, makes them a particular popular choice for freshwater tanks of all shapes and sizes. The male mollies are more slender than the female mollies and have a slightly longer tail fin, making the two sexes easy to tell apart.