Livebearers Unlimited: The Fancy Molly, Part 2: Proper Care and the Salt Myth

Author: Ted Coletti, PhD


The most spectacular freshwater fish that you’ve probably never seen is the fancy sailfin molly. The giant flowing dorsals of the males, its sail unfurled as it circles a female and both fish shimmer with iridescent scales, is a sight few hobbyists ever forget.


The rub here is that most pet shop samples are lethargic, clamped, fungused, overcrowded, or shimmying their way to death. As most hobbyists are not properly instructed on the care of mollies, the situation usually worsens upon arrival home. You can apply this same dilemma to the black molly, and to a much lesser extent other short-finned fancy mollies.


I feel every hobbyist should attempt a fancy molly tank at least once in their lifetime. Last month we discussed what a molly is and went through the various species and their behavior. For this last installment, let’s review what pet-shop and fancy mollies are, and how best to care for them. The answers may surprise you.


A History of Hybridization

Mollies are the common name for a subset of livebearing freshwater fish from the genus Poecilia, family Poecilidae. Poecilia includes several sub-genera or “clades,” such as Lebistes, which houses the popular guppy (Endlers or otherwise).


Mollies are part of the Mollienesia clade in which there are two complexes(sailfins and shortfins). There are about 20 recognized molly species, and the list is growing. Within these species there are numerous morphologically distinct races with slightly different colors and patterns. Within each race mollies tend to show a little variety in their sizes and shapes.


The fancy and pet-shop mollies you encounter are essentially hybrids of these various species, races, and morphs. This hybridization goes back to the late 1920s with fish farms like Crescent and Sunnyland. I always chuckle when pet-shop mollies are delivered for Breeders Award Program “points” at my local fish club and are called Poecilia sphenops if short finned, P. latipinna if high finned, and P. velifera if sail finned. They are all blood relatives! I advocate that fish clubs BAP programs create a “fancy” or “pet shop” molly class for points so as not to discourage the proliferation of the fabulous wild species that are true to their name.


The Salt Myth

The conventional wisdom, still touted in the media, is that all the poor health witnessed in pet shop mollies is because, by nature, they are brackish-water fish. In our pet shops and home aquariums they are simply not being provided indigenous water chemistry. Wrong! In nature, mollies cover habitats ranging from inland mud swamps to coastal lagoons. This makes it erroneous to make any generalizations about the “natural habitat” or “water conditions” of any pet-shop or fancy molly. Pet-shop or fancy mollies have been extensively hybridized over the past 80 years with species from a variety of habitats.


The latipinna (sailfin) complexof mollies, which get most of the grief from hobbyists and pet shop owners, are euryhaline species, which means they can adapt to a wide range of salinities. This is why many hobbyists and farms can use lots of salt with mollies and get away with it.


Note the words here: they “adapt to,” not “demand,” salinity. I have collected Poecilia latipinna in a saltwater bay in Key Largo, I have a friend who collects the same species in rainwater ditches in Louisiana, and I’ve met a Texas fish farmer who witnesses them swimming from rainwater streams to calcium-hard pools!


Is Salt Useful?

Yes, salt can help fish in poor health. Not just mollies. It is an old, cheap, non-toxic fishroom remedy that should be used more often by more hobbyists—but it is definitely not required for fancy mollies. Indeed, the use of salt will inhibit or prevent (depending on the dosage) a healthy growth of live plants, which go a long way to maintain the good water quality that mollies demand. That’s reason enough for me to not use it.


Fancy-molly pioneer and ALA Founder Dr. Joanne Norton addressed the molly-salt debate this way:


“If water changes are large enough and frequent enough, and if all the water is well aerated and circulated, livebearers (all the species I have kept) do fine without salt added to the water. If these conditions are not met, or if the fish are too crowded, then troubles appear. Thus, salt enables you to continue one or more poor tank management practices that are still harmful even though the fish may survive them in the presence of salt…”


Why Are Fancy Mollies Problematic?

The problem facing pet-shop owners and hobbyists regarding fancy mollies is three-fold in my opinion. And lack of salt is not one of them.


Genetic Degradation

First off, the Poecilia and related genera like Limia can suffer genetic degradation from extended line-breeding. Unlike the platies and swordtails (Xiphophorus), some of which have been line bred from pure species for nearly 80 years now, Poecilia tend to “break down” after repeated line breeding. This is best illustrated in the guppy hobby, where the breeders have to infuse their lines with new fish every few generations.


For mollies, it is well illustrated with the black molly, which I outlined a couple of years ago in this column. Legendary Florida fish farmer Bill Sternke had to continually introduce various wild molly species into his black molly strain as it became more susceptible to clamping and shimmying. Sternke’s diligence ended by the 1970s, and I am not sure if Asian or other Florida breeders have worked on strengthening the molly lines.


Acclimation Issues

The second problem facing pet shop mollies is the fact that many farms (not all) use lots of standard salt to dose their mollies either during raising or shipping. So when the mollies arrive in the pet shop and are quickly mixed in fresh water, there is an acclimation problem. Most veteran hobbyists know that quick acclimation from very different water conditions and temperatures is a great way to bring on illness in fish.


Difficult Water Conditions

The third problem arises from hobbyist experience that mollies are very demanding in terms of water quality. Charles Clapsaddle of Goliad Farms, one of the country’s largest fancy and wild molly hatcheries, provided me with some interesting insights. Charles does not raise any of his mollies in salt water. He finds they thrive from soft, near rain water to calcium hard salt water. But he does observe a very low tolerance for ammonia. Charles finds that “even the smallest amount” can result in clamping and shimmying.


Charles uses multi-stage vegetative filtration, utilizing plants like hornwort and Bacopa, to keep the water clean of impurities. I’ve been advocating this approach to my readers and in speaking engagements for many years. It is an “old school” way of keeping fish healthy (a result of the misnamed “balanced aquarium” concept) that is underutilized in this age of plastic plants and limited mechanical filtration.



So my hypothesis for the poor showing of pet-shop mollies (notably the shimmying and clamping) is:


1. Osmotic shock due to the quick transition from salted farm water to municipal pet-shop water after transit.


2. Ammonia buildup that has occurred during shipping.

3. Crowded and sub-optimal water conditions in some shop and hobbyist tanks.


How to Raise Good Mollies

Pick Winners

Your best bet when starting with fancy mollies is to select healthy stock. This can be difficult, as I have outlined already. But private hatcheries do abound, and there are better pet shops with good sources or occasional good stock.


Give Them Room

Prepare spacious quarters for your mollies. A 20-gallon long would be my bare minimum for a trio of large sailfins. I like to use a thin substrate of crushed coral or limestone “tufa” rocks to add the extra calcium. Several of us in the livebearer hobby have found the “calcium connection” and better substitute for salt, but as indicated, mollies can adjust to most water conditions. There are now special molly salts on the market that do not affect plants too much.


For fry to achieve their own grand size, you will need larger quarters or extensive culling. Dr. Joanne Norton used to use 30-gallon tanks for raising small batches of mollies and provided power filtration, which she observed created strong dorsals and fish overall.


Use Lots of Plants

Ensure good water quality by using copious amounts of plants. They not only take up ammonia and nitrite, but also nitrate, phosphates, and dissolved organic compounds. They will also serve as food and fry shelter. The best plants in my experience are the floating tropical hornwort, Najas, and anacharis (Egeria, Elodea, etc.). These are biogenic decalcifiers that can utilize the carbonates in your water for photosynthesis. Java fern and willow moss can be added as well. All these plants mentioned require no substrate, which will aid in keeping the water clean. You can add another good hard-water plant, Vallisneria spiralis, which will grow in just ½ inch of substrate. You can also add a cutting of pothos (devil’s ivy) houseplant to the (outside) top of the tank and let its developing roots grow through the water column.


Conduct Water Changes

Upon arrival home, drip acclimate your mollies to your tank water using an airline tube with a knot. You can add a tablespoon of salt per 10 gallons at this point, since they were probably shipped this way, but then over the next week slowly change the water over to your regular supply with small water changes. Ask the dealer what water conditions their mollies arrived in to guide you on initial water conditions. I like to start at temperatures around 80°F with new arrivals, and lower them to 70°F for wild species and 78°F for fancy strains.


After that, weekly or bi-weekly water changes of 25 to 33 percent are critical for fancy mollies. Make sure to use a quality ammonia neutralizer and provide biological filtration. Mollies benefit from an omnivorous diet, including frozen and live foods and some vegetable matter.


With this knowledge and diligence of care, your dream of a fancy molly aquarium can finally be realized. It will be a sight you will not soon forget!



Ted Dengler Coletti has been an aquarist and freelance writer for over 20 years. He resides with his patient family and guitars in the beautiful New Jersey Skylands, and is a Director of the American Livebearer Assoc. He is also a founder of the Northeast Livebearer Assoc. and Aquarium Hobby Historical Society. Contact for questions, suggestions, or thick, juicy steaks cooked just the way you like ‘em.