How To Breed Molly Fish: A Step-By-Step Guide

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Molly fish are pretty popular these days, mainly because they are incredibly beautiful and easy to care for. However, breeding them is a different story.

When I was still new to this hobby, I kept failing to breed a pair of mollies I had. No matter how hard I tried, they just refused to spawn.

Fortunately, over the years, I gained some experience in this field. Today, I will share everything that I know about this topic.

Let’s get started.

Also Read: Molly Fish Care Guide

How To Breed Molly Fish

From my experience, there are seven repetitive steps you can take if you wish to breed molly fish:

Step 1: Set Up A Separate Breeding Tank

Creating an individual breeding aquarium lets your mollies breed uninterrupted and free from the threats posed by other fish.

Proper setup of this tank is crucial to create a secure and favorable habitat for molly fish reproduction:

  • Tank dimensions: A 20-30 gallon aquarium is ideal for breeding molly fish, as it offers ample room for both the adult fish and their growing offspring.
  • Water specifications: Mollies flourish in water that is slightly on the alkaline side. Aim for a pH of 7.5-8.5 and a temperature between 78-82 degrees Fahrenheit. As for a heater, my recommendation is the Orlushy Submersible Aquarium Heater (link to Amazon).
  • Filtration mechanism: Opt for a mild filtration system. Mollies are fans of tranquil waters and strong currents can cause them undue stress. My recommendation: Hygger Aquarium Double Sponge Filter (link to Amazon).
  • Tank preparation: Before the introduction of molly fish, ensure that the tank is adequately cycled to promote the growth of beneficial bacteria. This process typically spans 4-6 weeks.
  • Aquarium decor: The aquarium should be layered with a soft substrate. Steer clear of sharp objects that could potentially injure the mollies.

Step 2: Condition The Breeding Pair

Mollies need to be at peak health prior to breeding, which can be achieved by feeding them a balanced diet and maintaining optimal water conditions:

  • Balanced nutrition: Offer mollies top-grade flakes, spirulina, brine shrimp, and bloodworms to boost their health and readiness to breed.
  • Feeding routine: Give molly fish several small meals throughout the day rather than one large portion. Overfeeding can lead to health complications.
  • Tank hygiene: Maintain the tank’s cleanliness by replacing 25-30% of the water on a weekly basis. Mollies favor hygienic surroundings.
  • Water parameters: Make sure that the water temperature and pH remain within the ideal range for mollies. Stable water conditions minimize stress.
  • Observation: Keep a close eye on the molly fish for signs of sickness or distress. Timely intervention can stave off health emergencies.

Step 3: Introduce The Mating Pair To The Breeding Tank

The careful introduction of the breeding pair of mollies to the new aquarium is a key step to kickstart the breeding process. Be gentle to avoid inducing stress:

  • Acclimation: Slowly acclimate the molly fish to the conditions of the new tank’s water to prevent shock.
  • Sex ratio: Stick to a ratio of 1 male to 2-3 females to prevent the male from displaying aggressive behavior towards a solitary female.
  • Behavior monitoring: Watch the mollies to make sure they’re interacting peacefully. Remove any excessively aggressive fish.
  • Patience: Give the mollies ample time to settle in and commence breeding, which might take several days.
  • Maintain conditions: Consistently monitor the water conditions and cleanliness to uphold a favorable environment.

Step 4: Provide Hiding Places And Plants

Plants and hiding places provide security and spawning sites for molly fish. These spaces also provide a refuge for fry once they are born:

  • Live plants: Include live plants like java moss and anubias. They provide natural hiding and breeding spots.
  • Artificial hideouts: Include caves or other decorative hiding spots. They offer additional protection for mollies and fry.
  • Plant density: The tank should not be overly crowded. Ensure there are open swimming areas for the mollies.
  • Maintenance: Regularly trim and maintain the plants to keep them healthy. Dying plants can affect water quality.
  • Fry refuge: Smaller hideouts and densely planted areas offer the fry places to escape from adults.

Step 5: Monitor And Remove Adult Fish

Watching the tank lets you notice when the female molly fish have given birth, and you can shield the baby fish or fry by taking the adults away:

  • Birth indicators: Look for a sudden uptick in tiny, quick fish. These are probably fry.
  • Separate adults: As soon as birth happens, quickly separate the adults to save the fry from getting eaten.
  • Adult care: Place adults back in the main tank and keep an eye on their health following breeding.
  • Cleanliness in tank: After the adults are removed, make sure the breeding tank stays clean for the fry’s survival.
  • Maintain records: Record the breeding details to help organize and handle future breeding activities.

Step 6: Separate The Fry From Adults

It’s vital to divide the molly fry from adults to guarantee their well-being and growth, as grown mollies might consume the fry. Here is how to do that:

  • Utilize a net: Carefully use a net to nab and part the fry from the adults, avoiding harm.
  • Second tank: Set up a distinct tank or breeding box for the fry, replicating the original tank’s conditions.
  • Group separation: House fry of close sizes together to stop bigger fry from hassling the littler ones.
  • Inspection: Frequently inspect the fry to make sure they are in good health and developing properly.
  • Timeline: Fry may be brought back to the main tank when they’re too big to be eaten by adult fish.

Step 7: Feed And Care For The Fry

Correct feeding and attention promote the healthy maturation of molly fry into mature fish. This it what you should know:

  • Fry nourishment: Offer the fry specialized fry food, micro worms, or finely ground fish flakes, giving them the essential nutrients.
  • Feeding intervals: Serve the fry little portions several times daily to aid their rapid growth.
  • Water changes: Carry out regular minor water changes to maintain cleanliness without troubling the fry.
  • Watch growth: Monitor the fry’s development to make sure they’re on the right track. Sluggish growth might indicate bad conditions or diet.
  • Modify care: As the fry mature, slowly alter their food and tank setup to match adult mollies.

Also Read: Molly Fry Care

Timeline For Breeding Molly Fish: What To Expect

If it’s your first time breeding molly fish, here is a simple table describing how long it usually takes for each step mentioned above:

Breeding StageDuration
Set Up A Separate Breeding Tank4-6 weeks (for tank cycle)
Condition The Breeding Pair1-2 weeks
Introduce The Mating Pair To The Breeding Tank1-3 days
Provide Hiding Places And PlantsImmediate to a few days
Monitor And Remove Adult FishImmediately after birth
Separate The Fry From AdultsImmediately after birth
Feed And Care For The Fry Until maturity(3-6 months)

How To Set The Perfect pH For Breeding Molly Fish

A slightly alkaline environment, with pH values between 7.5 and 8.5, is optimal for molly fish breeding. Ensuring such a pH will enhance their breeding success.

  • pH Adjusters: You can make use of commercially available pH adjusters to naturally raise or lower the pH level as needed. My recommendation: API PROPER pH 8.2 (link to Amazon).
  • Include crushed coral or limestone: If pH drops too low, both crushed coral and limestone can be used to boost it since they dissolve slowly, increasing pH.
  • Apply baking soda: You can also raise the pH using a little baking soda. But remember, use it sparingly to prevent abrupt alterations.
  • Water replacements: Frequent water replacements help sustain the pH. Ensure you use water with an already appropriate pH.
  • Prevent abrupt shifts: Molly fish can be stressed by sudden pH changes. Adjustments should occur over several days for a smooth transition.

Do Mollies Breed Easily?

Indeed, given suitable conditions, molly fish reproduce fairly effortlessly. As livebearers, they birth live offspring instead of laying eggs.

Here is what you should know:

  • Frequent breeders: Mollies are renowned for their high reproduction rate. A single mating can result in multiple reproductions because females can store sperm.
  • Pairing is easy: There’s no need for specific pairings for mollies to breed. Any healthy male and female have potential to produce offspring.
  • Minimal requirements: With appropriate water conditions, sufficient food, and enough space, mollies are likely to breed.

Can Molly Fish Breed In A Community Tank?

Although mollies can breed in a community tank, it’s not ideal due to potential fry predation and other fish interrupting breeding.

Consider the following:

  • Predation risk: In a mixed species tank, other fish may eat the fry, significantly lowering their survival rates.
  • Breeding interference: Other species might hinder the breeding process or compete with mollies for breeding areas.
  • Stress: Interactions with other fish could stress mollies, impacting their breeding ability or desire.
  • Control: Separately tanked mollies allow for better breeding control and success.

What’s The Breeding Frequency Of Molly Fish?

Female mollies can birth a new group of fry about every 30 days thanks to their sperm storage and continuous internal egg fertilization:

  • Sperm storage: Females can keep sperm for several months, allowing multiple births from one mating.
  • Regular births: Once a female starts to reproduce, she can birth new fry nearly monthly.
  • Breeding lifespan: Once sexually mature, a healthy female molly can continue to give birth for several years.

When Can Molly Fish Start Breeding?

Mollies can start breeding at around 3 to 6 months old. Exact timing might differ based on things like diet and water conditions:

  • Growth rate: A molly’s growth rate can determine when they start to breed. A healthy, well-fed molly may mature faster.
  • Gender differentiation: At maturity, gender differences become visible. Males grow a modified anal fin, or gonopodium.
  • Maturity size: When they mature sexually, mollies are typically about 1.5 to 2 inches long.

What’s The Gestation Period Of A Molly Fish?

On average, a molly fish stays pregnant for about 60 to 70 days. Factors like water temperature and the fish’s overall health can create minor fluctuations:

  • Stored sperm: Female mollies have the ability to save sperm for later fertilization, even if they’re not currently pregnant.
  • Fry batches: Depending on her size and health, a pregnant molly can give birth to anywhere from 20 to 100 fry in a single batch.
  • Pregnancy indicators: A swollen belly region and possible behavioral alterations point to a pregnant molly fish.

Also Read: Pregnant Molly Fish


For those in a hurry, here’s a quick recap of the information I discussed earlier:

  • Successfully breeding molly fish requires close observation of the aquarium setup, water conditions, and the health status of the fish couple involved in reproduction.
  • Establishing a separate breeding tank complete with hiding spots and plants is crucial for ensuring the safety and comfort of the molly fry.
  • Regular check-ups of the fish and timely separation of adults post-birth are vital to safeguard the newborn fry from potential predators.
  • Maintaining the right water pH balance, ideally between 7.5 and 8.5, is key for successful molly fish breeding.
  • Molly fish are known for their breeding productivity and can give birth to multiple fry batches each month once they’ve reached sexual maturity.