Poecilia sphenops – Common Molly
Poecillia velifera – Sailfin Molly

Origin: U.S. Gulf Coast to Central America – Mainly in brackish waters

Temp: 75 – 82°F (25 – 28°C)

pH: 7+ dH: Hard

Temperament: – Nonagressive, one of the least likely Livebearers to eat it’s own fry

Adult Size: Up to 4 in ( 10 cm)
Smaller for the common variety

Minimum Tank Size: 10 Gallon

Feeding: – Primarily a vegetarian but will accept most aquarium foods. A good algae eater, somewhat piggish.

Breeding: – A popular member of the Livebearer group of fishes. The female will drop live fry in intervals of between 4 and 6 weeks. Fry can be raised in the same tank with parents as long as no other species of fry eating fish are present.

Comments: Mollies like a little salt in their water are easier to keep in a species tank of their own. They seem to be prone to a variety of diseases when their requirments for warmth, salinity and higher pH are not met. Mollies are in fact a marine fish, I have caught many wild specimens in the Panama City Beach, Florida area, in full strength salt water. But they are highly adaptable and can live in fresh, brackish and marine conditions. Mollies are often used to break-in a new marine tank.
Sail-fin Mollies need plenty of room to grow to achieve the high Sail-fin and it will not usually develope in a tank smaller than 20 gallons and only then when there is only one or two fish. There is a multitude of varieties of Mollies, and all are easily interbred. If you want to maintain a pure variety they will have to be kept separate.
Mollies are especially prone to “shimmies”, this can be cured with the addition of 2 teaspoons of salt per gallon and an increase in temperature to about 80°F.

Note: Mollies are one of the best fish for taking care of an algae problem. I have found that they will eat even hair algae if you make them (don’t feed them much until the algae is eaten). Mollies are beautiful, hardy, unagressive but not timid, come in a large variety and are an all around nice fish to have in your tank. They would have to be high up in my top 10 list for aquarium fish

Female Gold Dust Molly
Female (Ma Molly) Gold Dust Molly

Male Gold Dust Molly
Male (Pa Molly) Gold Dust Molly

Baby Mollies
Baby Gold Dust Mollies, 1 day old, hiding in floating hair grass. Top view.
Baby Molly
Close-up of one of the babies, about a week old.