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Molly Care Sheet

Molly Care Sheet

Developed with and approved by a qualified veterinarian.

Molly Fish

This care sheet covers a variety of molly species, including:   

  • Black molly
  • Silver molly
  • Dalmatian molly
  • Gold dust molly
  • Marble molly
  • Balloon molly
  • Lyretail molly
  • Sailfin molly



Scientific name: Poecilia latipinna, Poecilia sphenops, Poecilia velifera 

Most mollies originate in North, Central and South America, where they reside in freshwater and brackish bodies of water. It is typically easy to tell the difference between males and females by the length and/or shape of their fins. These peaceful livebearers give birth to live young and can rapidly reproduce. Preferring to live in groups, mollies come in an array of colors, patterns and fin lengths. They readily adapt to changes in the water, making them a recommended species for beginning aquarists.


Typical appearance and behavior 

  • Mollies come in many different colors and patterns, including black, silver and orange, yellow, gray with dark gray spots, silver with black spots and moreStress can make the colors fade while some mollies will change colors, patterns and shades with age
  • They are social and do best when kept in schools of four or more, with one male per three females 
  • They are naturally peaceful; however, they can become aggressive if housed with aggressive fish and can be sensitive to overcrowding
  • Some aquarists have been successful in slowly transitioning mollies into a full saltwater environment; although, this is not the environment they are accustomed to and not recommended


Care Difficuty Beginner
Average Life Span Up to 5 years with proper care
Average Adult Size 3 to 6 inches long, depending on species
Diet Omnivore
Minimum Habitat Size 10+ gallons, depending on species
Water Temperature 72-82°F



Habitat size

Keep in an appropriate size aquarium based on the adult size of the species selected, which can range from 10 gallons for a couple mollies to a much larger aquarium for a school of mollies.

Building your habitat

  • Water health - Provide proper filtration to ensure optimal water quality to help maintain health. Slow to moderate water circulation should be provided to mimic water currents and high oxygen levels found in a molly’s natural habitat. Stable water quality (pH, ammonia, nitrate, nitrite) and water temperature are critical to the health of aquatic life. If you are unsure of your water quality, bring a sample to Petco for free testing. An aquatic heater should be used to stabilize water temperature, ensuring it does not fluctuate more than 2 degrees in either direction in a 24-hour period. Many mollies will benefit from the addition of freshwater salt to the aquarium; the specific gravity should be kept at 1.004. Always research your species-specific needs before adding freshwater aquarium salt. Do not allow specific gravity to fluctuate more than 0.001 in either direction in a 24-hour period
  • Decor -  Provide plenty of space for swimming as well as plants, rocks or decor for hiding places



A well-balanced molly diet consists of:

  • Food may be flakes, pellets, freeze-dried or frozen 
  • Mollies do consume moderate amounts of algae and will benefit from the addition of spirulina, algae sheets or wafers 
  • Offer a varied diet to ensure it is nutritionally complete

Things to remember when feeding your molly:

  • Depending on species and size, feed small amounts 1-3 times daily, no more than fish will eat in 1-2 minutes
  • Thaw frozen food before feeding


Molly care

  • Water care: Maintaining great water quality with regular water changes and adequate filtration is important to help keep your molly healthy
    • Daily: Check filter, water temperature and other equipment
    • Weekly: Test water quality at least once a week
    • Weekly to monthly: Change 10–25% of the total volume of water every 2–4 weeks, or as needed; change filter media monthly
  • Avoid overcrowded conditions; they are a major cause of stress and disease 


Where to buy mollies

Mollies are available for purchase at Petco online and in-store; availability varies by location. If visiting your local location,  please call ahead to check availability.




Tank mates 



Signs of a healthy molly

  • Clear eyes
  • Healthy appetite
  • Bright, even coloring
  • Clean in appearance
  • Free of parasites or disease

Red flags (If you notice any of these signs, contact your local aquatic specialist or aquatic veterinarian)

  • Loss of color or appetite
  • Spots or fungus on body or mouth
  • Erratic swimming
  • Frayed fins
  • Labored breathing
  • Weight loss
  • Bloating
  • Cloudy eyes or pop-eye
  • Listlessness


Health Issue Symptoms or Causes Suggested Action
Health IssueFin rot Symptoms or CausesFrayed or disintegrating fins; the base of the fins usually reddens. Suggested ActionImprove water quality; consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueIch or velvet Symptoms or CausesWhite spots appear on fins and body; fish rubs against hard objects or swims erratically; rapid respirations. Suggested ActionQuarantine fish immediately; add freshwater salt and use a commercial ich remedy as directed;. consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueFungus Symptoms or CausesWhite cottony growth and/or discoloration of the eyes. Suggested ActionQuarantine fish; use a commercial antifungal remedy as directed; consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueBacterial infections Symptoms or CausesCloudy eyes, open sores and/or reddening of the skin. Suggested ActionImprove water quality; add freshwater aquarium salt; use a commercial antibacterial remedy as directed; consult your local aquatic specialist or aquatic veterinarian for treatment.
Health IssueCottonmouth or columnaris Symptoms or CausesCottony white growths along the body and/or gills, frayed fins and gills turn brown and necrotic in late stages; caused by bacterial infection. Suggested ActionQuarantine fish; improve water quality; lower aquarium temperature to 72°F to deter bacteria from growing; medicate as directed; consult your local aquatic specialist or aquatic veterinarian for treatment.



  • How long do mollies live? Mollies live an average of up to 5 years in the home aquarium with proper care.
  • What do molly fish eat? Mollies are omnivores and should be offered a variety of flakes, pellets, freeze-dried and frozen foods. Mollies also consume moderate amounts of algae and will benefit from the addition of spirulina, algae sheets or wafers.
  • How long are molly fish pregnant? The gestation period for mollies is typically between 40 to 60 days.
  • How many babies do molly fish have? Mollies can have between 40 and 100 babies.
  • How big do molly fish get? Mollies average between 3 to 6 inches, depending on species. 


Additional care sheets

Notes and resources

Ask a Pet Care Center partner about Petco's selection of products available for the care and happiness of your new pet. All products carry a 100% money-back guarantee.

Because all aquatic life are potential carriers of infectious diseases, such as atypical mycobacterium and salmonella, always wash your hands before and after handling your aquatic life and/or habitat contents to help prevent the potential spread of diseases.

Pregnant women, children under the age of 5, senior citizens and people with weakened immune systems should contact their physician before purchasing and/or caring for aquatic life and should consider not having aquatic life as a pet.

Go to the Centers for Disease Control at for more information about aquatic life and disease.

The information on this care sheet is not a substitute for veterinary care. If you need additional information, please contact your veterinarian as appropriate.