For those of us who started the aquarium hobby as children, the magic of that first tank or bowl may never be equaled. Yet the diversity and majesty of our childhood favorites lives on in the livebearers. From the simplest feeder guppies to the most elaborately adorned sailfin mollies, the world of livebearers offers a variety of shapes, sizes and colors to custom fit any freshwater community aquarium.

Mollies
Native to the mangrove swamps and estuaries of Central and South America, these fish have been introduced to the southern United States, as well as throughout much of Southeast Asia. The mollies comprise a large portion of the family Poeciliidae, a group known for its tolerance of brackish and saline environments. Mollies are very salt-tolerant, and millions are produced annually for the commercial pet trade in coastal breeding preserves that are fed entirely by the ocean.

Many saltwater hobbyists use mollies, particularly black mollies (Poecilia sphenops), to feed their groupers, sharks, eels and other carnivorous fish because of the molly's ability to stay alive and well in saltwater. A batch of feeder goldfish dropped into a reef tank will last for only a few minutes before going belly-up, if they are not eaten immediately. But a batch of salt-acclimated mollies will thrive in a marine tank for as long as it takes the predatory fish to consume them.

Ironically, it is this salt tolerance that makes the molly somewhat unsuitable for a community freshwater tank. They have specific water requirements and demand a good degree more attention than the typical freshwater community fish. Water temperature of 68 to 82 degrees Fahrenheit and a pH of 7.0 to 8.0 are critical to a successful molly aquarium. Although these fish can live their entire lives in freshwater, an addition of aquarium salt (5 ml/4.5L will benefit your mollies in a number of ways: healthier slime coating (which is crucial in protecting against parasites), full finnage and lower stress levels.

Mollies do best in a mature planted tank that has been cycling and healthy for several months, and which provides plenty of cover. Dropping a couple of conch shells in the water will also help - as these calcium and silicon shells break down, they will help to maintain a high pH and will release some amount of oceanic salt into the water.

Diet is also crucial. Although these fish thrive consuming live mosquito larvae and other aquatic insects, they also consume a surprising amount of plant materials, such as leaf matter, root tips, algae and any other bit of aquatic greenery they can find. In the home aquarium, it is paramount that mollies get sufficient plant matter. Algae disks or flake foods for omnivores are best, while slices of zucchini squash (frozen then thawed to break down the cell walls and make it digestible) dropped into the tank will also make for a fine, if not a little messy, vegetarian feast for your mollies.

Mollies are selectively bred for color, size and fin adornment; and it seems like a new strain is coming out every few months. All things considered, however, there are only about three molly species that show up on the market, with more than a dozen different morphs of each species. The black molly has been selectively cultivated to form "sub-species," such as the green molly, liberty molly and Mexican molly. The black molly itself is the result of cross-breeding. In its native Central American waters, the black molly is a sort of dull gray color that might warrant the name "charcoal molly."

One of the most unusually patterned of the mollies is the dalmatian molly, which is a cross between the black and white mollies. The drawback to this beautiful fish is that in generating its peppered appearance, breeders robbed this fish of its vitality, making it less hardy than most other mollies and more prone to diseases such as ich, body fungus and fin rot.

A particularly striking member of the family is the sailfin molly, the large dorsal fin occurring in two species. The larger of the two is the giant or Yucatan molly (P. velifera), which may grow to lengths of more than 6 inches. It is not as often seen on the pet trade as is its counterpart, the common sailfin molly (P. Iatipinna), which may only reach 4 to 4½ inches. More often encountered than either of these species are cultivated forms that result from cross-breeding with other mollies. Such "manufactured" varieties include the albino molly, golden sailfin and lyretail molly, which is a form of black molly.

Not the most prolific of the livebearers, mollies tend to brood every eight to 10 weeks (instead of four), but may birth as many as 130 to 150 fry. Just remember to feed your mollies a hefty amount of vegetable matter if you want them to breed. Although it is not fully understood, the reproductive chemistry of these fish will not properly operate without a plant-rich diet.

Guppies
The second large group of Poeciliids is the guppies. Originally restricted to northern South America, Trinidad and Barbados, these fish now hail from all corners of the globe. Introduced to some new areas when they survived being flushed down the toilet, a great number have been reputed to thrive in the sewer systems of southern cities, thus flushed fish may not actually die, but go on to live in recycling ponds, streams and other bodies of water. These fish were also purposefully released in New Zealand and the southern and central United States as a form of biological pest control intended to eat mosquito larvae. These guppies have successfully taken their place within these ecosystems.

Guppies are hardy fish that are far more tolerant of varied water conditions than their molly cousins. Given a proper acclimation process, these fish may also take to life in saltwater. A stable pH of 7.0 is best, although gradual dips or rises of no more than 0.5 pH are tolerable. Guppies also require ample filtration but without a powerful current - it is difficult for these weak-finned fish to fight strong currents. A bio-wheel style filter that can cycle three tank volumes per hour is recommended (although an undergravel/ airstone filter combination worked for me for a number of years with no problems).

Like mollies, guppies have been the subject of selective breeding that strives to attain genetic perfection in the areas of color, fin formation and overall aesthetic beauty. Almost all guppies seen in the pet market today are variations of the wild guppy (Poecilia reticulata). Different wild populations of guppies had different characteristics (for example, those found in brackish waters sported flowing fins, while stream varieties had shorter, rigid fins), and these were exploited by commercial breeders. Line breeding produced especially colorful and flamboyantly finned fish to such an extent that guppy societies have formed around the world to collect, catalog and set up their own breeding standards. Some of these cultivated varieties include the triangle, veiltail, fantail, lyretail, roundtail, speartail, top/bottom swordtail, double-swordtail, coffertail and bannertail. With so many breeding bloodlines available these days (although many are not found in the typical fish store), there is no shortage of variety for the discriminating aquarium hobbyist to choose from.

Guppies are omnivores that thrive on a combination of plant and animal material. A captive diet consisting of tropical flakes is sufficient to keep them alive, while a more vegetation-rich regimen will give your guppies superior color and prepare them for successful mating. Many professional breeders have tanks that are overgrown with algae. While the average fishkeeper may not want the walls of the tank covered in green slime, these fish will benefit greatly from a diet rich in algae. Leave the pleco at the store, and watch your guppies grow fat from devouring the algae that grows in their tank!

If you do wish to have both robust guppies and a clear tank, drop a few live plants, such as Amazon swords (for example, Echinodorus amazonicus, E. bleheri, and E. cordifolius) in the aquarium. Your guppies will nip tiny bits of decaying greenery off the leaves, thereby supplying their need for vegetation, while at the same time keeping your plants neatly preened and healthy.

Breeding is not a difficult task with guppies. Males have a noticeable gonopudium (the elongate fin situated between the anal fins), and grow no larger than about 1.2 inches. Females, however, are a good bit larger: 1.8 to 2 inches. Under ideal conditions, guppies are prolific fish that will brood every four to six weeks and may drop as many as several dozen fry. The largest brood I ever heard of numbered close to 70 fry.

Platies and Swordtails
Of all the livebearing fish in pet shops today, none holds such a special place in my heart as the platies. Among all the danios, mollies, hatchets and neon tetras I had over the years, one red platy survived to see them all come and go. He lived for more than seven years and died at a whopping 2 inches long, the average being less than 1½ inches. Belonging to the genus Xiphophorus, the platies and swordtails hail from Mexico, Belize, Guatemala and Honduras. They are robust fish that are hardy and tolerant of a wide range of harsh conditions.

Their toughness makes them a fine choice for the beginning hobbyist, while their vibrant coloration can add a touch of beauty to any aquarium. Like guppies and mollies, platies and swordtails are subject to color variation within different populations of the same species, and are selectively bred for these traits. The cultivated forms - and there are a lot of them - tend to grow larger and live longer in the aquarium than wild species.

When purchasing platies or swordtails, look for smaller, less developed individuals with shorter swords and smaller stature. These will be the youngest of the bunch and should provide you with a more rewarding experience. The older, larger fish that are still in shipment may be more aggressive or stressful toward tankmates once you get them home. Large adults can also be violently territorial, often nipping or harassing other fish. It is best to select smaller individuals, so they can "grow up" in your tank.

Both platies and swordtails are suited for life in the community aquarium. The fancy varieties (such as the lyretail swordtail, hi-fin swordtail and swordtailed platy) may prove somewhat problematic in a tank of fin-nippers, such as tiger barbs. These flamboyant fish may be targeted and harassed by their tankmates, and might do better in a species tank or one that is large enough to grant each fish its own territory.

Swordtails, as noted, may demonstrate a degree of aggressiveness toward others of their own species, as well as other tankmates. This is especially true of males. One male, therefore, should be housed with a number of female swordtails or alone. Providing one male with a harem of females will go a long way in curbing his aggressive tendencies. Most platies, on the other hand, are tolerant, mild-mannered fish that can easily coexist with a wide range of other tropicals.

Platies and swordtails thrive in a neutral to slightly basic pH (7.0 to 7.5), and benefit greatly from a planted tank. As is true with guppies, platies and swordtails will nip and pick at these plants to augment their diet, but will also accept flake foods, tablets, lettuce, peas, bloodworms, mysis shrimp and other tiny crustaceans/aquatic larvae. Although most do not have the tiny frame and weak fins of fancy guppies, these fish do not do well in tanks with a lot of current. Less powerful filtration, such as bio-wheels or trickle systems, is best, as these fish thrive in calm, peaceful waters.

Although platies and swordtails will breed in captivity, their propagation tends to be a bit trickier than most livebearers. Male swordtails are distinguishable from females by both their gonopodium and sword projection on the tail fin. Do not be fooled, however - some males may go their entire lives without ever growing a pronounced sword. Reliable sexing is attained only through the absence or presence of the gonopodium. The females of both platies and swordtails also exhibit a darkened patch toward their vent, which expands or contracts based on her degree of pregnancy; very pregnant fish will exhibit a very large dark patch.

These fish tend to mate with just about anything they can get a hold on and can easily hybridize, thereby rendering the offspring infertile. This occurs when too many generations of the same bloodline continue breeding. When successful broods are produced, the fry are quite fragile and may be physically stunted if not given a sufficient amount of a proper diet.

If you wish to breed either platies or swordtails, set up species tanks designed for breeding. These tanks should be large (20 to 55 gallons) because the developing fry need a great deal of space if they are to mature without physical deformities. Fry may be reared on the same foods as adults (ground-up flakes, shrimp nauplii, brine, and other minute foods are appropriate).

When the fry of these or any other species of poecilid emerge, they will need hiding places to feed and grow. If left in open water, these minuscule fish will almost certainly be eaten. Mature clumps of Java moss will work just fine. The moss provides cover for the fry, while at the same time affording them plenty of vegetative food. The only major drawback with all poeciliids is that if housed in poor water conditions, these fish are prone to contract whitespot disease (ich) and other bacterial infections. If caught soon enough, these problems are easily treatable, but are even more easily preventable through regular water changes and responsible husbandry practices.

Other Poeciliids
The world of livebearing fish does not end with mollies, guppies, platies and swordtails. Despite the wide variety of these fish, there are more poeciliids that might have a place in the aquarium. Inhabitants of the southern United States, Central and South America, and the Caribbean Islands, they come from a range of habitats. The spotted tail or true mosquitofish may live in mountain streams at elevations of more than 8,200 feet, yet it fares equally well in brackish coastal waters at zero elevation.

The remaining poeciliids also represent a broad spectrum of sizes and lifestyles, ranging from the diminutive and docile merry widow (Phallichthys amates), which grows to no more than 1 inch long, to the highly predatory pike livebearer, which reaches nearly 8 inches in length and sports an imposing mouthful of needlelike teeth. In common with the rest of the Poeciliidae family, these remaining members are an excellent choice for the young or beginning hobbyist. They are hardy, beautiful fish (even the pike livebearer, despite its propensity for carnage, is a blue-green gem to behold) that can add color and variety to any aquarium.

If you do decide upon one of the lesser known poeciliids, it is worth your while to research your choice before bringing it home. Make sure it will coexist with your tank's current inhabitants and that you can fulfill its captive requirements. Some species of poeciliids are prone to jumping at night or when they get nervous, so it is best to keep the tank covered at all times.

Some of the best suited of these fish to the community aquarium are true mosquitofish (Heterandria bimaculata) and the slap-sided blue-eye (Priapella compressa), while the bishop fish (Brachyrhaphis episcopi) and the knife livebearer (Alfaro cultratus) are nervous, edgy fish that are more difficult to keep in captivity. With the exception of the pike livebearer, all species of Poeciliidae are omnivores, and all can benefit from the diet described for the guppies or platies.

The poeciliids are a wonderful family of fish with a great deal to offer to the hobby. Many are colorful, elegant creatures that add a bit of spice to the average tank in their natural or cultivated forms. Given a little know-how on the part of the hobbyist, almost any species or combination of livebearers can thrive for years in the home aquarium.