OWNING TROPICAL FISH - THE LIVEBEARERS / MOLLIES
The Livebearers - Mollies
Mollies are popular even though the most desirable of them are much less hardly than the other common livebearers. Perhaps the relative ease of maintenance of some of the mollies - such as the molly, Poecilia sphenops - makes potential purchasers of the larger and harder to maintain sailfin mollies, Poecilia velifera and Poecilia latipinna, think that they'll have the same level of success with the sailfins that they did with the sphenops. Unfortunately, it usually doesn't work out that way.
Easy to keep or tough to keep, mollies are commonly offered for sale. They come in degrees of black (ranging from a beautiful velvety solid black down to the miserable blotchiness of a "marble" molly), golden, albino, chocolate and even reddish-orange colors, with and without modified finnage in the form of lyretails and veiltails.
At their best, sailfin mollies are magnificent - big, bold, showy, colorful, vigor-radiating fish in which the males can unfurl an enormous banner of a dorsal fin and ripple it in its majesty while posing across a female's or a rival male's, path. At their worst, they're shaky, wobbly, fin-clamped zeros huddled in a corner waiting to die of some piscine pip. If you ever want to know what a tropical fish hobbyist means when he says a fish has the shimmies, just a sick molly.
Mollies like warm water and can't stand chilling at all, so make sure they're given continuous warmth of no less than 72 degrees F, with 78 degrees F being ideal. They are reputed to need more vegetable matter in their diet than other livebearers require, and special dry foods with high vegetablen contents are available for them.
Baby mollies are bigger and bulkier than other livebearers, but they're also slower-moving and less active. Luckily for them, their parents are less likely to eat them than other livebearer benefits from being netted and moved when she's heavy with young, but female mollies seem to suffer most from such treatment. Also, female mollies are the least amendable to being enclosed in livebearer breeding traps; they're much better off in a heavily planted tank.
All of the mollies do better with some sea salt (half a teaspoonful per gallon for sphenops and Yucatan sailfin mollies, a full teaspoon for regular sailfins) in their water, which is one reason they do best if kept in tanks by themselves, not mixed in with other species.
The common name molly, often gives as mollie, comes from an old name for the genus: Molliienesia which in turn was derived from the name of the French naturalist Frederic Mollien.
My advice: stay away from the mollies, at least the sailfins, until you've gotten some experience in the hobby and have developed a feel for giving fishes what they need; lay off mollies until you know what you're doing. But if you still want them after you've mastered and fundamentals, get yourself a couple of pairs or trios of the biggest and best sailfins around and let them put on a permanent show for you.