Setting Up a Livebearer Aquarium

Livebearers are among the hardiest and most colorful freshwater fish in the aquarium hobby. Their peaceful nature and constant activity make them popular with fish keepers, young and old. Livebearers get their name because they give birth to live babies instead of laying eggs like most fish! They include guppies, mollies, platies and swordtails, as well as goodeids, halfbeaks and anableps. This article deals with guppies, mollies, platies and swordtails, which are the most common livebearer types found in aquarium shops.

Origin

Guppies, mollies, platies and swordtails belong to the Family Poeciliidae and are found from the southern United States, through Mexico and Central America, to northern South America. Guppies are also native to Trinidad and Tobago, Barbados and other Caribbean islands. Wild forms are usually not as colorful as captive-bred strains, as decades of selective breeding have produced an amazing variety of colors and fin types. In recent years, the Endler's Livebearer (Poecilia wingei), a previously little known relative of guppies that is native to northeastern Venezuela, has become popular. Due to its small size, it is a perfect addition to desktop aquariums.

Water

Livebearers adapt to a wide range of water conditions, making them perfect for beginners and experienced aquarists alike. They do best in moderately hard to hard water, with a pH above 7, and will thrive in most conditioned tap water. Water temperature should be in the mid 70's to low 80's. Since many types of livebearers are native to coastal brackish environments, some experts recommend adding a tablespoon of non-iodized aquarium salt per 5 gallons of water, and even more for mollies. Others feel that minerals like calcium and magnesium that make water "hard" are key to keeping their livebearers healthy. Before adding salt or any other additive to your aquarium, make sure the other tank inhabitants will tolerate it.

Diet

Most livebearers are omnivores and should be fed a variety of quality flake, pellet and frozen food.  Mollies are more herbivorous, so a little extra spirulina or other vegetable matter in their diet will result in better growth and color. Guppies and Endler's Livebearers, on the other hand, are more carnivorous, so be sure to include brine shrimp, daphnia or other protein-based food in their diet.

The Aquarium

Choosing the best aquarium for your livebearers will depend on which types you want to keep. The rule of one inch of adult fish per net gallon works well here. With that in mind, a 3 to 5 gallon aquarium will safely house a trio of Endler's Livebearers or fancy guppies, a 10 gallon tank is sufficient for platies and most mollies, but you will need a minimum of 20 to 30 gallons for swordtails and sailfin mollies due to their larger size.

A heater is mandatory, unless you live in a tropical climate. Many livebearers become inactive and can be more susceptible to disease if their environment is not warm enough. Keep a secure cover on the tank to reduce evaporation and prevent fish from jumping out – especially swordtails, which can be quite jumpy! 

HOB (hang-on-back) and internal filters are perfect for smaller aquariums, but if you intend to breed your fish (they sort of do it on their own without your help anyway), consider placing a sponge prefilter over the intake to prevent babies from being sucked in. Canister filters are a good choice for aquariums of 50 gallons and larger, with the same sponge pre-filter placed over the intake strainer.

Provide plenty of structure in the form of decorations, driftwood, rockwork and plants. Live plants like Hornwort offer surface cover and valuable hiding places for newborn fry, as well as females seeking refuge from the mating behavior of over-zealous males. Live plants also help oxygenate the water and reduce algae growth by consuming nutrients such as nitrate and phosphate.

Tankmates

The perfect tankmates for livebearers are other livebearers, but there are many other choices.  Rainbowfish are a great option as they are peaceful, active and many types do well in hard water. Tankmates in a livebearer aquarium should be tolerant of hard water and salt if you choose to use it. Choose community fish that reach the same size as your livebearers and avoid fin-nippers like Tiger Barbs. Ask your local aquarium shop expert for additional help in selecting tankmates for your livebearers.

Breeding

Livebearers are among the easiest aquarium fish to breed because they do all the work. It is easy to tell males from females, it is fairly obvious when females are pregnant, and the young are relatively large compared to other fish species. They are born fully developed and free-swimming, ready to eat just about any food you offer.

Male livebearers are typically smaller and more colorful than females. This is especially true with guppies and Endler's Livebearers. Besides being larger, females in this group are virtually colorless except for their tails, while males have longer, more vividly colored tails and more colorful bodies.

Male swordtails are easy to distinguish from females, as only the male has the tail extension that gives them their name. Male sailfin mollies have a larger, more extended dorsal fin that gives them their name; females are considerably larger than males, with shorter dorsal fins. Male standard mollies are smaller than females and usually have longer dorsal fins.

Male and female platies are a little more difficult to tell apart at first glance because they are closer in size than other types of livebearers and have fewer distinguishing characteristics. That said, all livebearers can be sexed by their anal fins (the fin behind the belly) once they reach maturity. The female's fin is fan-shaped or triangular, while the male's is modified into a rod-like structure called the gonopodium, which is used during mating to fertilize the female.

Female livebearers typically have a dark area toward the back of the belly called the gravid spot, which becomes larger and more noticeable when they are pregnant. Note: the gravid spot can be difficult to almost impossible to see in some livebearers because many varieties are darker colored or black. When females are heavily pregnant and close to giving birth, you can sometimes see the babies' eyes peering through the gravid spot!

Male livebearers like this Sunset Platy have a rod-like modified anal fin called the gonopodium.

All livebearers should be kept in ratios of 2 to 3 females per male to reduce stress to the females from the constant and sometimes aggressive mating behavior of the males. Provide females with plenty of refuge in the form of plants and other decorations.

Some types of livebearers – particularly guppies – are prone to eating their own young, oftentimes as soon as they are born. Other tankmates will think nothing of a tasty snack, as well. To prevent this, many hobbyists place gravid (pregnant) females in breeder nets or "traps" to give birth, removing them once the babies are born. The young can then be raised separately from the other fish until they are big enough to be safely added to the main fish population.

Guppies, mollies, platies and swordtails are hardy, peaceful, active fish that come in almost every color in the rainbow. They adapt to a wide range of water conditions and accept almost any food you offer them. And most of them are easy to breed, which is especially fun for kids. Perhaps it is time you gave livebearers a try!

The dark gravid spot is easy to see at the rear of this pregnant guppy's belly.