KEEPING MOLLY FISH IN AQUARIUMS

The Molly is from the same Genus as the guppy and Endlers livebearer; Poecilia and the family: Poeciliidae, the same as other livebearers.
Mollies wild habitat consists of fresh, brackish, and coastal waters from the Carolinas to Texas and the Yucatan Peninsula of Mexico. Mollies do not have any one exact habitat in common, especially salinity (despite some misconceptions here). What they do have in common is water high in alkalinity, Calcium and General Hardness.

Mollies only thrive in water that is very high in GH and Calcium (a GH over 250 GH), pH over 7.8, KH over 100+, and some salt, about 1 teaspoon per 1 gallon or 3-4 liters (or 1.002 to as high as 1.006 specific gravity). Mollies can easily survive in a specific gravity (salinity) of 1.012 which will not support parasites such as “ich” that may infest them at lower salinities.





What many hobbyists do not understand about mollies and their natural habitat is that although salt is very useful for disease prevention, it is the other ingredients in Marine Salt that really make a difference in molly health, and that is Calcium, Magnesium and the many other trace elements available here.
What all Molly habitats have in common is hardness/high mineral water, NOT salt!
Understanding this will go a long ways in keeping healthy, happy mollies. Without proper calcium, Magnesium and other essential elements in the water as well as a healthy Redox, you will most likely have trouble maintaining a healthy Molly population in your aquarium. With the right parameters, Mollies can be one of the easier fish to breed and keep and be very enjoyable fishy pets.

Maintaining correct Calcium and other necessary element levels will aid in healthy osmoregulation which will in turn result in healthier more disease resistant fish.
You can maintain Mollies in a community tank with many but only the most sensitive South American Fish. Other livebearers that do not have as high of mineral requirements will also do well in an aquarium that is at least kept to minimum Molly requirements.
If you intend to keep Mollies in a community aquarium with other fish such as Platties, Gouramis, Ect; here are the minimum requirements I would suggest:

*pH – 7.5-7.8
*KH -100 – 150 ppm
*GH – 200 -300 ppm (important!)
*Salt (marine salt is best here) – 1 tablespoon per 5 gallons to 1 teaspoon per gallon

Here are a few products I would suggest for maintaining these levels:
*Wonder Shells; these are great for maintenance of GH, Calcium, Magnesium and other essential elements and are also safe and in fact quite useful for general community tank essential element maintenance.

*Sea Chem Buffer (Marine OR Freshwater);this is useful for increasing KH and maintaining a safe AND BALANCED alkalinity/KH level (unlike Baking Soda!). Please see this article for more about this subject: “Calcium, GH, KH, pH, & Electrolytes in Aquariums”

*Aragonite, oyster shell or crushed coral in a filter bag; of these aragonite is the best, however all are poor at to reacting to rapid changes in water chemistry that can affect GH and KH which is why I recommend the first two more (although in a well maintained, non over crowded aquarium, rapid changes should be uncommon).

SUMMARY:

Mollies can be interesting and colorful fish for your freshwater aquariums. Usually these are hardy fish except when the water conditions they require are not present, especially mineralization and to a lesser degree salt. Mollies can do well in a community tank with other fish provided the right water parameters are present. I do however caution adding Sailfin mollies to aquariums less than 20 gallons (75 liters). Smaller molly types such as black, balloon, goldust, ect., will do OK in 10 gallon aquariums. Keep in mind that a poorly maintained aquarium of ANY size cannot hold as large or as many fish.
Also note that mollies (as with all livebearers) can be prolific breeders and unless you are prepared for their offspring, it is best to have only male mollies (single females can still to store unused sperm from the male fish in her body for several months through a process called "superfetation").

For further reading I recommend these articles:

* “How do Fish Drink; Proper Osmotic Function”
* “Calcium, GH, KH, pH, & Electrolytes in Aquariums”
* “Aquarium (& Pond) Redox Potential”
* “Wet Web Media; The truth about mollies"