Mollies, one of the more popular aquarium fish, come from Poecilia spp. and the Poeciliidae family. Similar to the swordtail fish, Mollies come in a variety of shapes and generally grow up to 4-4¾ inches in size. The males are usually smaller, growing mostly to 3 to 4 inches.
Apart from their difference in size, you can tell male Mollies from the females by the difference in color, and gonopodium.
Although well-suited to estuaries, these fish can live in a very broad range of habitats, although their preferred water temperature is 72 degrees to 82 degrees Fahrenheit. Mollies also prefer hard water with added salt, with a pH level between 7 and 8.
The fish also like lighting and thin layers of humus, along with plenty of places to hide. Hence ornaments with caves and ‘hidey-holes’ and plenty of plants are preferred.
Mollies are omnivorous and will feed on a range of vegetables including spinach as well as algae. They are a lively school fish, so it’s best to have a minimum of three mollies in your aquarium (more is better). They also require a constant water flow.
These fish are livebearers and fairly easy to breed.
Guppies – Poecilia reticulata – are part of the Poeciliidae family, found in areas around Guyana, Venezuela, Brazil, Trinidad, and Barbados. They prefer very gently flowing, hard water with a temperature between 68 degrees – 75 degrees Fahrenheit. As with Mollies, the pH level should be between 7-8.
Also similar to Mollies, Guppies prefer well lit tanks with plenty of plants and ornaments. This species will eat all sorts of foods, again very similar to Mollies.
Guppies tend to prefer loose school with their fellow species and will be constantly active. They tend to breed well, however will eat their young and so should be removed to a separate tank as soon as possible after the young are born.
