Magnificent Mollies

Author: Bill Allen

There are an incredible number of mollies out there with different body colors, body shapes, and fin types. One livebearer enthusiast breaks it down so you can even breed your own strain.

My 50-Year Hobby

“Da lady at da fish sto’ tol’ me dat da big black one is pregnant and gonna have babies soon,” so said my Cajun uncle Bobby from Lafayette, Louisiana, when he presented me with a few fish right after Christmas more than 50 years ago. Uncle Bobby had seen the 10-gallon aquarium that I received as a Christmas present and wanted to buy a few fish for my new hobby.

My parents were less than thrilled by this news. They wanted only male fishes for my new tank so it wouldn’t be overrun by additional fishes. But, just as promised, the “big black one,” a robust female black molly, soon delivered about a dozen tiny, plump babies. They were removed from the aquarium and placed in a small plastic container, and the rest, as they say, is history. So began my relationship with livebearers in general and mollies in particular, which has lasted over 50 years.

Mollies are among the most common fishes in any local fish store, and for good reason. They come in an astonishing array of colors, sizes, and fin shapes. Some of the wild varieties are a bit finicky and can be a challenge to find and keep, but many of the domestic varieties are very hardy and can stand quite a few of the mistakes that beginners might make.

Two Types of Mollies

The name “molly” is derived from their previous scientific name, Mollienisia. Mollies are now lumped into the genus Poecilia, which includes guppies and limias (a relatively uncommon Caribbean livebearer), among other lesser-known fishes. You can still find references to Mollienisia as the genus in which all mollies belong in some of the older aquarium literature.

Sail-Fin Mollies

Mollies can be separated into two groups: sail-fin mollies and short-fin mollies. The sail-fin mollies consist of three species: Poecilia velifera, P. latipinna, and P. petenensis. P. latipinna is native to the southern United States, from South Carolina to Texas along the Gulf Coast. My hometown of Shreveport, Louisiana is home to wild sail-fin mollies, although this area is not cited in any of the standard references and we are hundreds of miles from the coast. The wild green sail-fin molly was among the first small fishes kept in captivity.

The other two species of sail-fin mollies, P. velifera and P. petenensis, are both from Central America and are not native to the US. Pure examples of these species are difficult to find; they are usually available only from specialized breeders.


The males of these species have beautiful high, broad dorsal fins that they display during their elaborate courting dance. Unlike the finnage of hi-fin swordtails, platies, or fancy guppies, these big, beautiful fins are a natural trait and not the result of domesticated breeding programs. Watching several male sail-fin mollies vie for the attention of a female in a well-lit tank is a thing of beauty. An even greater treat is to see the males do so in the wild.

Males will also spar and chase one another, but permanent damage is seldom done. Being a flashy dancer and dresser for the ladies has a high cost, however; it also attracts predators and raises the fish’s chances of being eaten by them! So, some male mollies never develop the beautiful broad dorsal but instead keep a low profile, schooling with and mating with the females. These are called “sneaky” males (Luckner, 1979).


In the wild, all three of these species have a greenish-gray body color. When courting, the males will flash brilliant blue and their bodies take on a gold overcast. But in the wild, sometimes the occasional fish can be caught with black markings.


One reference cites an aquarist named “Crescenty in New Orleans” as breeding the first black mollies (Jacobs, 1973). However, I don’t believe that a man named Crescenty ever existed. Instead, several breeders worked on the project independently in the late 20s to early 30s, one of the first being Bill Schomberg of Crescent Fish Farm (see the similarity?) in New Orleans. Contemporaries of Mr. Schomberg remember him having black mollies “as big and fat as Polish sausages.” Schomberg also caught and sold wild sail-fin green mollies. Other commercial fish farmers breeding black mollies included Florida fish farmers Jack Beater and Bill Sternke (Socolof, 1996).

Short-Fin Mollies

The second group of mollies is short-fin mollies. The males of these fishes never develop the broad, high dorsal of the other three species. Even the females have a shorter dorsal fin base than the females of the sail-fin species. At one time, most short-fin mollies were collectively called “Poecilia sphenops,” but in the last few years, the scientific splitters have been at work dividing the shortfin mollies into several different species, including P. mexicana, P. latipunctata, P. salvatoris, and more.

Fancy Domesticated Varieties

All of the mollies in both of these groups readily hybridize with each other, yielding possibilities for the dedicated selective breeder. Mollies have occasionally hybridized with their close relatives, the guppies, although the offspring appear to be sterile and thus not useful as breeding material. To the best of my knowledge, mollies have not been crossed with swordtails or platies. It is very doubtful that any of the fancy types described below have swordtail genes in their pedigrees.



Even in nature, mollies are sometimes found with black blotches. The blackest fish were bred to each other until a solid black fish was developed. In the process, quite a few mollies were found with varying amounts of random black blotches. These mollies are called “marbled mollies” and are available as a color form today. I have also seen marbled mollies sold as “salt-and-pepper” or “Dalmatian” mollies. When the black coloration is arranged as streaks rather than blotches, the fish is often designated as a “harlequin.”


Marbling can also be found on many of the other colors described below, so you can find marbled gold mollies, marbled 24-carat gold dust mollies, and so forth. The amount and placement of the blotches varies tremendously from one fish to another, and when these fish are bred to each other, babies ranging from solid black to no black and all variations in between are produced.


Albinism is a trait expressed when no color pigment is produced. True albinos are a golden-yellow color. The hallmark of a true albino is pink eyes. Some of these fish also retain bright iridescent flecks, which give them a truly wonderful appearance. These flecks, called iridophores, differ from normal pigment cells and are thus not affected by albinism.

A Florida fish farmer once told me that albino mollies are difficult to raise in outdoor ponds because their bright color, combined with poor eyesight, makes them easy prey for wading birds, the scourge of outdoor fish farmers. This story may be apocryphal, but it makes sense.

Although true albinos have pink eyes, some fish display a reduced but not total lack of pigment. These fish are called “leucanistic” or semi-albino. My favorite of these fish is the gold molly, which has the beautiful yellow-gold coloration of an albino but still has dark eyes.

Gold Mollies

Some gold mollies appear to have scales edged in red. This unusual but very beautiful color is called “sunburst.” I’ve seen sunburst mollies with golds that are almost cream in color. A similar color is called “creamsickle,” which is almost identical to that of the frozen confection.

Silver Mollies

Sometimes all pigments except one are eliminated. This appears to be the case of the silver molly. Since the natural form of the molly usually has a silvery background with green and some other colors, eliminating all pigment except the silver results in a fish with a pure silvery color.

24-Carat Gold Mollies

Another beautiful gold-colored variety is the 24-carat gold molly. Most of these I have seen appear to be of the short-finned, possibly the P. sphenops, variety. This is a very bright, almost shiny, gold color that appears to be quite different from the gold molly previously described. The dark black eyes on this fish stand out remarkably against the shiny gold body. Many 24-carat gold mollies that I have seen have varying amounts of marbling, which is very attractive against the gold background.

Chocolate Mollies

I have also seen mollies with a brown, not black, coloration that is almost identical to a chocolate Labrador retriever. Not surprisingly, these fish are called “chocolate mollies.” There are even some mollies with red in them, which is very unusual. I am not sure how this color variety originated.

Fancy Finnage

As magnificent as a sail-fin molly is, the sail-fin trait is found naturally in wild mollies. There is great variation in the size of the sail fin, but it is still a natural trait. In much of the older literature, mention is made of the difficulty of obtaining really nice sail-fin mollies in captivity, but it can be done. It appears that the mollies need uncrowded conditions and good water quality. Dr. Joanne Norton once recommended six to eight in a 30-gallon tank. Good male sail-fin mollies also need a longer time to mature (Norton, 1975).


In addition to the natural sail-fin trait, there are several finnage varieties that have been produced from “sports,” or mutations, that have been carefully fixed and bred into other mollies. In the lyretail, the top and bottom ends of the caudal fin extend beyond the middle of the fin, similar to a lyretail swordtail. The best specimens display a wide, clean arc with no broken, bent, or damaged fin rays. But although lyretail swordtails are usually unable to breed because of deformities in the gonopodium (modified anal fin that constitutes the male sex organ of most livebearers), lyretail mollies generally are able to breed.

Veiltail Mollies

Also available are veiltail mollies that have a large, wide tail similar to the tail of a veiltail guppy. In a really fine specimen, the tail can be as much as 2½ inches wide. I have also seen the word “guppytail” applied to veiltail mollies but am uncertain as to whether this is a separate trait or simply another word for the same trait. In a 1973 issue of Livebearers,Dr. Norton published a hand-drawn chart illustrating these different fin types, which has remained similar since then (Norton, 1973).

Color and finnage are inherited separately, so just about any color can be bred into just about any fin shape, thus increasing the number of possible molly varieties.

Balloon Mollies

An unusual man-made variety of molly is the balloon molly. This is a small molly with an extremely distended abdominal cavity. Some aquarists treat these fish as deformed freaks and state that keeping them is cruel. The balloon mollies I have seen are as healthy and lively as any other mollies. It might be wise to be careful placing them with other aggressive fish, as their distorted body shape may limit their ability to feed. Simply keep an eye on them and be sure they are getting their share at meal time (Glass, 1997). Once again, the balloon trait can be bred into other molly finnages and color traits, once again increasing the number of molly varieties.

Good Golly, Many Mollies!

If you are a beginning aquarist, you will be fascinated by the colors and varieties of the mollies at your local pet store and will surely find one that can pique your interest. If you are a seasoned old hand, you can keep one of the more exotic wild strains of molly or try developing and fixing your own unique fancy strain. Wherever you are in this hobby, there is definitely a molly for you!

Works Cited

Glass, Spencer. 1997. Mollies: Keeping and Breeding Them in Captivity. T.F.H. Publications. Neptune City, NJ. 64 pp.

Jacobs, Kurt (translated by Gwynne Vevers). 1973. Livebearing Aquarium Fishes. T.F.H. Publications. Neptune City, NJ. 321 pp.

Luckner, Carol Louise. 1979. “Morphological and Behavioral Polymorphism in Poecilia latipinna Males (Pisces: Poeciliidae).” The Louisiana State University and Agricultural and Mechanical College.

Norton, Joanne. 1973. “Molly Fin Types.” Livebearers: Bulletin of the American Livebearer Association 2(2).

Norton, Joanne. 1975. “Livebearer Questions.” Livebearers: Bulletin of the American Livebearer Association 22.

Socolof, Ross. 1996. Confessions of a Tropical Fish Addict. Socolof Industries. Bradenton, FL. 62 pp.

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